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Im finally starting to piece together my car, got everything together but dont wanna start it until i know of all the things that i wanna know haha.

I have an Adjustable Fuel Pressure regulator for my BP-Turbo, im running 450cc DSM Injectors and a Walbro 255lph Pump. Also 10 psi of boost to start what should my fuel pressure be?

Are you running a resistor box for those DSM's?
Check resistance of your old injectors and those of the dsm's they may be different.

wooo..luckily its the same and theres a few guys running them aswell

Fuel Pressure can be a double edge sword. It also depends on what your using for engine management.

Remember...as you raise the fuel pressure your injectors will flow more BUT your fuel pump will support less power. As pressure rises, the fuel pump flow decreases. The Wahlbro flow starts to fall off steep some where around 60psi...its been a while since I've seen the flow charts. Wahlbro also has a "Hi Pressure" 255 which is designed to keep the flow from falling off steeply until the 70ishpsi mark.

My car for example runs 30psi of fuel pressure at 0 in/hg of vac. and only around 22-24psi at idle (1400-1500rpm). at 30psi of boost this puts me at 60psi of fuel pressure which is the optimal flow rate of my pump (110gph@60psi...or a smidge over 416lph@60psi). The reason my car is set up this way is to make it both easier to idle on the 1000cc (96lb/hr) injectors and to also make sure I don't venture into a unknow flow range of the fuel pump at peak power which would result in possible lean out.