This may be a stupid question but im new so....anyway, are blow-off valvels ONLY needed if u have a manual transmission and nitrous on the ur ride?

 

No, and no, a blow off vavle is for a turbo system, it's there for when you building pressure then let off the gas so the remaining pressure has some where to go other then back into the turbo and slowing it down and hurt it, you can have one on an automatic tranny, and with nitrous but you don't need either of them, but you do need a turbo system for a blow off valve

 

also for superchargers.

 

blow off valves for turbo and superchargers(turbine superchargers only).