Saab Tips
Performance Tips
The first upgrades you should consider is a more free-flowing exhaust system, a K&N Drop-In Filter, and an APC (Turbo Chip) upgrade.
If you plan to have the car for awile, then get a stainless steel exhaust system, it should outlast your car. Free flowing exhausts give the car a real nice rumble too. I used to have the Swedish Dynamics K&N Filtercharger kit and I can say honestly that it sucks. You do get better flow with it, but you also get ALL the hot air of the engine rushing into your intake. I highly recommend either having custom work done (Moving the filter into the wheel well), or getting a K&N Drop-In Filter replacement (K&N Part No. E-2457 Saab 900 Turbo). This way you keep the stock ducting (For cold air) and you also get the benifits of a free flowing intake.
The turbo's have 2.5 bar fuel pressure regulators. (900's that have been upgraded at the dealership (Red APC) will have a 2.8 bar FPR) Simply going to the junkyard and grabbing a FPR out of a Naturally Aspirated 900, or buying one from the dealership will yield you a 3.0 bar FPR. Some of the perfomance company's in my links section also sell these items. Upgrading the FPR is something you should consider after you have upgraded the exhaust, APC and air filter. If your going to do this, you should probably upgrade your fuel injectors at the same time. If you plan on going all the way with your saab, you would more than likely be more pleased with a rising rate FPR, which you can get from Swedish Dynamics or SPG9 (I got mine from SPG9 and it works great, but thats not to say that the Swedish Dynamics one is not just as good).
I've found (At least on my Saab) that perfomance ignition wires really do make a difference. Some companys also sell a new ignition coil with thier wires (I can't vouch for these because i do not have one, YET). I've heard that an MSD ignition is a nice upgrade (www.twinsaabs.com), but I can't vouch for this either, YET.
If you own an older Classic 900, and you plan on buying a new transmission, you should definetly consider buying a transmission of a newer year (up to 93). The newer transmissions have bigger pinion bearings, as well as upgraded 1st, 2nd, and reverse gears. If you are planning on rebuilding your tranny, Swedish Dynamics has a kit that allows you to upgrade the pinion bearings yourself. You can also use the transmissions out of Naturally Aspirated 900's on turbo models. The N/A trannys have different gear ratios, and will allow higher speeds in each gear (Aprox. 10mph). The downside to this is you WILL lose a little speed off the line, but if you set up your cylinder head, APC, Turbo etc. to kick out real power after 2500 RPM, your car will FLY once the turbo kicks in.
There is no point in having a fast car if you can't stop it, so your next upgrades should be in the braking system. First you should check your calipers. If your brake pads are constantly wearing unevenly, then you might have to rebuild/replace on of your calipers. Slotted rotors are what I have and they work great. I've heard that cross-drilled rotors are also good. Slotted and/or cross-drilled rotors promote cooling, prevent warpage, and help dissipate water. Having large open rims also promotes cooling. As for brake pads, that's really a personal preference. I use kevlar brake pads. They work good and have low brake dust (A must with chrome rims).
So now your going fast and stopping quick. Now you need to do some suspension work. Start with your shock absorbers. I use bilsteins and haven't had a problem yet. I haven't heard anything about any of the other brands of shocks, but I know of several dealerships that have been selling bilsteins to performance minded customers for years. Its a good idea to check all your bushings for wear when your putting your shocks in. Having good bushings all around will really tighten up the handling of the car. Please note: You will feel more of the road with these shocks, so don't expect it to feel like riding in Grandma's Buick. Next you should think about new springs. There are alot of springs on the market out there, but I would trust Saab with this one. Go for the SPG springs (Gold or Bronze paint on spring). They will lower the stance of your car slightly, and they are just a bit stiffer but take a sharp corner and you'll know why. Larger rims will have a good effect as well. You'll feel more of the road, and they help cool the brakes. I would recommend going with Ronal U.S.A., they are an OEM manufacturer for Saab. I would urge you not to go with a company like Tire Rack. I had a set of thier rims and I have been pulled over repeatedly because they are too wide. Not to mention the damage they did to my fender flare kit (Hit a bump, tire hit fender flare, fender flare hit pavement, Nuff said).
When replacing the cylinder head on a turbo, I would recommend going with a 2.1 head off of a naturally aspirated 900. If your gonna do it anyways you might as well squeeze as much power out as you can. I would also recommend using a copper head gasket if you plan on running higher than normal boost pressures.
Turbo Upgrades. I have ordered a t3/t4 hybrid from Swedish Dynamics. They tell me Garrett Research like to take thier sweet time with things, so the turbo is on back-order. I'm not going to comment on this until I have mine and have a chance to test it out. After all, I wouldn't just blindly recommend something unless I have it or have tried it.
Exterior Tips
It is my personal opinion that the Classic 900's look best with an airflow or replica airflow kit on them. Or at the very least and SPG kit. The Saab OEM airflow kits are difficult to find, but if you can find a set in good condition, by all means grab it. A fiberglass replica is available from Erebuni Corp. but be warned, this is not something you can do in your backyard. These are just fiberglass shells, they have no brackets on them, and they will need to be shaved/added to by a good bodyshop. Be sure to check with the bodyshop to make sure that they have Fiberglass experience. It's also not a smart idea to lower your car too much with these bumpers installed. If you live in an area with lots of steep hills you could damage the bumpers. Be careful when parking as well, I've had a few occasions where I wasn't paying attention to the height of a curb and scraped the bottom of the bumper a bit.
Saab side skirts are best found in the classified section of The Saab Network. Buying side skirts new from Saab will run you $300 per panel. If your really lucky you might be able to find a SPG at a junkyard that you can grab panels off of. It's recommended that you buy new decor strips for the panels. Most Saab dealerships will more than likely have trouble finding the part number for this so here it is: 69-14-352. When installing side skirts you will want to buy new plastic nuts for the door panels, and you will need to buy new rivets. If any of the rails are bent, they will need to be replaced. Remember: The panels slide on. Trying to push them on with brute force is only going to bend a rail.
A fender flare kit is simple enough to find. The part Number is: 02-45-365. These look great and will really add a nice touch to your Saab. These will fit with stock bumpers, but you will need side skirt to install them.