Ran for codes and got a PO171 (o2 senser) cleaned the MAF and hoping that works.
Seems like its bucking under load. Anyone have this problem?

Take a look at this. https://www.gmforum.com/t284972/ Does this sound like your problem?

not realy, more of a hesitation/loss of power under harder acceleration

I'm having the same problem with a 99 GP GTP, I'm thinking deposits in the injectors, or the air filter

Can you get your car scanned? I had a 99 here a while back that would have a loss of power as you pulled from a stop. It was hitting 20* of knock retard. Never found the problem, the guy never came back. But I suspected it was a bad knock sensor.

thinking of trying injector cleaner and fuel filter. MAF senser in $150

Unplug the MAF, the engine will stumble a bit while it settles in on running on the tables instead of live data. then drive, but nothing more the 50% throttle. If the engine runs the same, the MAF is fine. Test fuel pressure, if your loosing pressure it could be a fuel pump.

I will have to take it and scan sometime, its my brothers car but it wouldn't surprise me beacuse the kid that had it didn't take care of things that he should have and replaced random things that don't go bad

Good idea but it is somewhat intermiten

P0171 is my favorite code.

First thing to know. This is not an O2 sensor code. The O2 sensor is reading the fueling and the pcm is reporting to you that for unknown reasons the pcm is adding fueling beyond the normal amounts and has been instructed to tell you of the issue.

The usual suspects in this code are vacuum leaks, battery cables being corroded or evap lines being hooked up backwards.
TB gasket, vacuum connectors, EGR to LIM tube etc for the vac leaks, check battery cables by pulling the cable and removing the boots to check for corrosion under then and inside the sheath of the cable itself, for the evap, trace the lines and follow the underhood diagram for proper routing.

Could also be the maf, my experience usually leads to one of the above though.