FAST LSx intake and throttle bodies... 78mm vs 90??

Not sure if this is the right section for this, if not, sorry, please fix :)

I've recently decided I'd like to get a FAST intake and a new throttle body for my car. I'm still considering the LS6 but I'm just curious about the FAST at the moment. Problem is I'm hearing and reading a bunch of varied comments on which size to go with. I'm stuck and was wondering if someone could shed some light onto the subject for me (yes, I did search and am continuing to do so, it isn't helping too much). Anyone with either, what are some pros/cons?

My car is a '99 z28, a4 completely stock for the catback and a lid/filter. I'm basically figuring out as I go what I want to do with it, I want to probably do headers next and eventually heads and cam, not sure anything more specific than that yet.

Any info I really appreciate, thanks a lot and sorry if this is a subject that's beaten to death here!

spend the money once and get the FAST 90/90. if you are going to go heads/cam later it's worth it. if you port the 90/90 you will gain even more. i started with the Ls1 intake, now i have the Ls6 intake and i'm saving for the FAST 90/90 now. nothing wrong with the Ls6 intake, but i want more TQ and i know the 90/90 will help give me that...

I have heads/cam in my C5 and just finished putting the FAST 90/90 on. Immediate difference in more power, untuned.

I like the FAST 90/90 system setup but it's just way out of my price league at the moment. I'll see what happens as far as searching for either goes and take it from there...and save $ in the meantime

If money was not an issue, and you are planning heads/cam in the future, then the FAST 90/90 would be the way to go IMO. BUT...the LS6 intake and a ported stock throttle body would make huge gains from stock and it is (relatively) inexpensive as far as mods go. The ported stock TB and LS6 intake also flow well enough to support most head/cam mods you would do in the future as well. Just my $.02