An intercooler is a heat exchanger for the hot air that comes out of the turbo. Intercoolers allow you to cool the incoming air. Cool air takes up less space. This means that you can force more air into the engine and add more fuel and get more horsepower. The length of piping doesn't really make much difference. The bigger the intercooler the better.

This is my setup which uses a Saab 900 IC. For this installation you will need to move or remove the stock radiator overflow tank that is next to the AC compressor and the charcoal canister. I used a bungee cord attached to the frame rail to hold the intercooler in place. It installs nicely because it has both connections on the same side. It does a great job of cooling. I run 20 lbs of boost with no detonation. And I still have AC. The pipes are from Lowes hardware. They are aluminum electrical conduit 90 degree pipes that are coated with something inside them that makes it feel like teflon, off the shelf items. Make sure you clean the inside of the pipes before installing, mine had paint inside them. You have to shorten one pipe to make it fit.You need to add one piece of straight pipe also. I had some Volvo IC piping around that I used to make that piece. The elbow for the intake is from a Saab or Volvo.

There are some pics of this intercooler next to a new Passat intercooler at the bottom.

Saab IC Piping

You can see that I have removed the heater valve in this picture. Look for the green silicon hose near the firewall. You will see two long pieces of hose and one little short one. I cut off the top of that steel pipe and put a 90 degree on it with a small piece of green silicon hose. This makes it easier to run the hoses.
I did this because I had a heater valve go bad and almost leave me on the side of the road. It can't do that now. I changed all the hose to silicone so that the cooling system of the car doesn't have any weak parts.
You will not get heat in the car unless you turn on the fan. The temperature adjusting switch will still work. This is because the heat is adjusted by the air vent. It lets in all cold outside air if you turn the lever to the cold position.

Saab versus Passat Intercoolers, The Saab is the smaller one