Tony, I switched and the Victor was I think 5/8 to 3/4" taller. I don't think it was an inch. I had to redo the foam seal on my air pan, but I don't think it was that much. The Victor is taller and straighter runners, I have had a hard time getting good idle quality like I had on the M1. Maybe my engine is too mild for what is probably better suited to higher rpms (max HP @ 6600) .600 flat tappet, stg. 6 mild port, 11.4 comp. Anybody else have idle trouble with the Victor? I can't give you performance change cause I also backhalved the car over winter.