sometimes it will prime to 43psi and stay there but when I accelerate psi drops down to 39psi and below and sometimes it goes to 43psi and drop to 0 in seconds. the fuel pump is new, could it be the fuel pressure regulator?and I will pull the fuel rail 2morrow

 

sounds like it might be a fuel pressure regulator to me.

 

pulled the fuel rail off. there was some gas by injectors 2,4. all other injectors were dry around manifold. I am replacing my fpr, should I take this time to replace injectors also?

 

Have you primed it with the rail off and can look to see an injector leaking? By priming I mean to just turn the key on and off, on and off, finishing with it in the on position(don't start...just on position).

 

naw I didnt, but fpr and injectors are the only thing that hasnt been replaced. What size injectors are the stock size and who are some good injector makers

 

The stock injectors I think are 24 lb. Stock replacements from GM are good unless you're planning on upping the power, then you could look into SVO or Racetronix. Both of them make them up to 60 lb I believe. Anything other than what you have right now (24 lb) you will need to reprogram the PCM though.

 

I might go with new SVO 24#

 

I changed the fuel press. reg., installed new FMS SVO 24# injectors and same problem. On acceleration she stumbles/hesistate .but my fuel pressure is @ 45 and stays in that range so my f pressure is better .what else could this be. FYI(ALL NEW PARTS): opti is new AC Delco, Walbro fuel pump,the fuel tank was cleaned before I installed the fuel pump,fuel filter,new coil,Icm,Wp,plugs,plug wires(I checked for burned wires),TPS sensor , Bosch O2 sensors 2 weeks ago The problem really started after the O2's.

 

check the air filter, my brothers car did the same thing with his kn filter

 

can you elaborate on this? do you mean that the filter may be dirty? this is the first time i'm hearing a kn causing our infamous low rpm stumble. what did your brother do to solve it?

 

his sounded like it wasnt getting enough air so i told him to recharge the filter and clean the maf screen. the filter was new 7 or 8 months ago. when ur at idle is your engine shaking alittle, sounds like we are having the same prob iv replaced everything on that motor and it still sputters at idle. when u snap the gas with ur hand on the intake what does it feel like

 

yea it does do that putter like its clogged up or something but I dunno, this car is pissing me off! I unplugged the MAF and it still does the same thing.i have the Lt1 crome elbow with some pvc pipe and a 180 elbow into a K&N filter. It was working fine also before problem started but all that is new as well

 

UPDATE:

I noticed when the MAF is plugged in it runs worse than if I had it unplugged

 

still searching for answers......

 

it seems like you are changing too many parts too quickly. You said the fuel pressure was crap, then you changed the pressure reg and injectors. Now you still have a problem but we can't be sure if it's the same one. try changing one thing at a time.... maybe.
the fuel pressure should be some value (39-49?) when primed then should drop a few ponds when the pump shuts off (should drop 3-10psi) it should be the same pressure at idle (the lower pressure) and then the higher pressure at WOT.
someone correct me if I am wrong