Which CAI when installing a FAST on a 2000 C5
I personally have a 102 and I NA. I had to get a piece of silicon that was not reinforced with the threads inside it. The silicon was 4" and the 102 is like 4.25". Since the silicon was not reinforced it would stretch to fit the larger diameter of the intake and still be small enough to fit the other tubing. I have a 4" diameter aluminum short spacer to fill in the gap from the intake to the intake bridge. If you are boosted you will most likely not be able to use a piece of silicon that is not reinforced. Being NA I don't collapse or explode the silicon that is not reinforced. There are places online that sell stepped silicon connectors. Do some googling and I am sure you will find them. They are not cheap either.
They sell different couplers that work just fine. 
