[Frank12]

What is the best intake manifold and throttle body setup (not trying to spend that much on it) to get a little more air flow (around 90mm opening) for my 408 paired with the APS twin turbo kit. Must fit under the regular hood and the Fast intakes are not an option as they are 2 piece. Should I just port my ls1 manifold and throttle body?

 

[Nothubertjfarnsworth]

kind of wondering why you want a 90mm opening when you are using an ls1 style throttle body. you might just want to get an afternarket 90mm+ 4-bolt style cable driven throttle body. i think edelbroke makes one that will work with bolt bolt patterns, but it will not fit under your hood.

if you just want a manifold that performs better than stock and works with the stock throttle body, weiand looks like it makes a decent manifold.

 

[Kfxguy]

90MM VS 85MM VS 78MM will make ZERO difference with a turbo. Ported stock intake would be good. The fast intake ive heard doesnt hold higher boost pressures from WHAT I'VE READ. I have 2.5" charge pipes on mine so my 92mm throttle body is pointless.

just port your stock intake and leave the throttle body alone. Theres no power in porting it because its going to be forced in and thats not the restriction.

 

[Mick Naughty]

What boost are you trying to do? Don't see an issue with a fast.
Volume becomes the factor going with larger stuff. Especially going with a big motor.
I assume you are cathedral head even considering using an ls1 intake, I also assume you mean ls6.
Id you want to go cheap, stick with what you have as the whole top end will be a restriction.