okay according to my flow calculations if they are correct then stock throttle body flows more then the maximum amount of air your engine can suck in... here are my calculated findings...

65mm will flow 558 CFM <----stock size throttle body
70mm will flow 601 CFM <----about $230 on ebay for this throttle body
75mm will flow 644 CFM <----about $270 on ebay for this throttle body

a 4.6L @ 6000RPM will need 487.3 CFM
a 5.4L @ 6000RPM will need 572 CFM

so when it all comes down to it... even boosted your stock throttle body engine can actually use. do to the air being compressed not under normal atmospheric conditions.

so save ur money throttle bodies dont help u much.. best just port ur stock one unless u just wanna buy one for looks

 

i would have to disagree. If your logic was correct then adding a larger than 65mm t body on a mustang 5.0 or 4.6 would not add horsepower, but they do. You may have forgotten the a fuel injected motor can go over 100% efficiency. That said i would bet that a larger t body would make more power as long as if fit the intake tract but it wouldnt be that much.

 

I agree, this doesnt line up with how things work in the real world. Many (modded) trucks get a performance increase from a larger throttlebody.

For example, Lightnings, Neal's truck, etc etc.

 

only reason the larger throttle body will help u is releif air restriction. and keep the motor from having to try as hard to suck air through the small hole. thats only way they help and why u see little gain. my whole point was its not worth the increase in size for the price u pay for it