The first two pictures in the sequence below are of the setup I made for my intercooled 86 GN. Total cost came to about $25 without the flexible 4" hose. I had a piece of hose laying around for some time but I don't know what its cost was. I used 1 - 3" to 4" rubber coupling for the MAF connection and used a PVC reducer to connect the 4" hose at one end and then used the other end to connect to the 4" side of the rubber reducer. At the other end of the hose is a straight 4" union. The hose connects over this union and the 3" K&N fits inside of the other union. Screws are used to secure the filter to the union.