89 5.7 iroc / 57k mile - wife surprised me w one that looks great. Owner thought the driving issue was a fuel filter or pump.

idles fine, sounds fine w throttle while in park. Under a load it runs terrible. No power when u mash the gas and it stalls. I replaced fuel filter, no change. Inspected MAF, it looks new (Delphi brand). Just curious if anyone has ideas before I find a shop.

 

As you mention, could be fuel pump. Symptoms sound fuel pressure related. Checking the fuel pressure would be my first step.

 

probably fuel pump - easy to check pressure with a schrader valve gauge

 

Agree it sounds fuel related.... A clogged fuel pump inlet for me resulted in similar symptoms....mine had rust pickup from the tank...

Don't expect a Delphi maf to be a good thing though... They have known issues... Mostly that they don't read correctly at low airflow... I had to fake mine out to get the car to run right ... Ended up finding an original Bosch... Greatly improved the performance....