How To: 350Z 75mm Throttle Body Install 

From what research I've done on this for my charger and g37 which i did get 75mm throttle bodies for the gains with just the throttle bodies aren't much. I did the upper and lower manifold and the z1 3 inch intakes at the same time so i don't know how much they helped specifically, company claimed 10 whp, they cost over $600 though. They were also a pain in the ass to fit in especially with the 3 inch intakes. Personally if i could go back i probably would have put that $650 elsewhere but I'm not unhappy with them, they look good and they do help some I'm sure, especially with the bigger intakes.

Paired with forced induction they'd do a lot better.

​@@sneakypete2656 It's just that the diameter is going to be limited by the plenum and intakes anyway, so if you don't upgrade the plenum and the intake manifold it's really not actually adding much diameter. I think with doing the upper manifold and air intake (larger pipes) it likely would help a bit assuming there aren't flow issues exhaust wise, but really think it probably should be one of the last upgrades done IMO after everything else is good.