how much pressure should i run on a 305

 

60 psi Max. Probably about 50psi is good, if you have an adjustable fuel-pressure regulator.

 

Thats like asking how fast should I drive on the street? We have no idea because we dont know the rest of the info about your car. Every car is different and likes different pressure. There is no magic setting that works with every car. Stock is around 42 PSI, and higher pressures have shown good results, but higher pressure also means more fuel is being injected into the engine. Since the stock calibration is already rich at wide open throttle, injecting more fuel makes the engine richer. So, start with 42 PSI, and increase it in 2 PSI increments until you stop seeing positive results. And, you should do this on a dyno or at a dragstrip so you can see exactly what your changes are doing. You wont be able to feel a 3 or 4 hp increase or decrease.

 

it is stock only mods are cat back flow master under size pulley's k&n filter's and a hot prom chip

 

I would agree with kevin91z but I would start at 40psi. Your mods with the afpr will net you maybe 8-10hp. That's if your lucky. You will have a hard time feeling that. It is the same as an airfoil. Not really gonna feel it. You'll be happy you got it though when you do more mods.