Engin sputtering at 3k Rpm
 

My mustang is sputtering when it gets to around 4k rpm. I read a repair manual, and decided to test the fuel system pressure. It reads right at the min. level 30psi w/ vac , 40 psi without. I decided to try and test the hold pressure of the system. Assuming that I am following the directions. It read that the system shoud stay pressurized after the engine is shut off. If this is so, It drops to 0 the second the key is turned off.
What I am getting at is did i do the test right?
If so what are some of the solutions to this?
Any help would be great.
Thanks, Steve

What kind of mods have you done? The FP at idle should be around 40, maybe more if you have stock injectors and some mods. The only mods I had on my car at one point were a full exhaust, cold air intake, and timing to 15 degrees. I was having the same problems you are having, mostly in 4th gear. I got a adjustable FP regulator, and it solved my problem. My advice would be to get an adjustable FP regulator.