Read this Induction dyno. Its a dyno between a bolton Gt with a mac CAI (fender), and a full C&L setup (CAI, TB, plenum). And they also have a 70MM vs 75MM TB dyno too. They tuned the car with an optimizer shrug: never heard of it before reading this)...it JUST changes the A/F ratio by manipulating the MAF.
I attached the dyno graphs. The 75MM TB caused the car to go rich shrug: ) and it still made about the same as the 70. When they leaned it back out, it made more. So apparently the 70 makes more power vs the 75 when untuned...but when you tune it then the 75 is better. Thats probably why everyone syas 70 = N/A and 75 = S/C. GET THE 75MM TB! I got the 75 also. You will need a tune anyways as that stuff will lean you WAY out.