20-25psi Max, I could peg a 30lb gauge with the plate forward. cruising I saw 5-7psi at 70 mph, with surges to 12psi up hills empty. the stock wastegate should open around 25psi. I put a 60lb gauge on before i did some other mods and lost my turbo. The max i got was 37psi with 100 plate all the way forward with the stocker. With my Super-B i see 43psi max and i tow alot. don't see anything above 1300*F, even if I try to. The stock HX35 is efficient below 30 psi, anything above that and you get really hot air. However, ALL of this is with a standard not an auto.