Z22hy Rev only to 4K

[parsj022]

Hi,
I had a bad hpfp according to live data so I replaced the diaphragms inside and now I am reading around 730psi idle and 1000-1300 psi under load. However when I rev the car up about 3.5 it will get to 4K then stumble, shudder then if I keep pumping the throttle it sounds similar to running it with the throttle body bare of the air intake pipe like that low tone noise. Then if you let go quickly the engine will shake like crazy. Restart the car then it’s fine.
Could this be anything to do with swirl flaps?
Im not pulling any codes from the engine module at this time either

 

[KevinH]

It could be the swirl flaps, but have you checked the FPR (Fuel Pressure Regulator). I believe these have a habit of misbehaving and were a Vauxhall recall along with the Siemens HP pumps which were replaced with the Continental type.

Fuel Pressure Regulator (with gasket) - GM Part # 95507060 (supersedes part # 24404015)