I've noticed in searches, and just being on the board, that most people go with the fast 90, or the LS6. Wouldn't the fast 78 be a good inbetween compromise? Anyone ever run it?

 

I think the reason not too many people use the 78mm FAST is that it is expensive and does not offer that much of a gain over the LS6 . Too little gain for too much money !

 

Hardly any gain over the LS6 for hundreds of dollars more.

 

I had one out of the first batch that I ran up 'till this last season. As stated above performance is good, on a par with the LS6 but it's double the money. The only real advantage is that you can take it apart, install the lower, and port match it to your ported heads. Can't do that with a LS6 intake.

 

Oh doesn't really seem worth it.. I figured it was the same as the fast 90 but just more restricted at the TB.

 

You figured right, the throttle body inlet IS the only difference. It's a 3 piece manifold. The 78mm and 90mm share the same lower and middle parts, and the only difference between the two is the upper shell, which is interchangable.