Intermittently engine starts to stall when accelerating

I originally had put a post before and I just wanted to share the solution to my problem in case anyone else has this problem. My original post said "have the car listed above that has been running great but randomly it starts to want to stall. I can be driving with the pedal at a constant position and I will randomly feel loss of power as If I just let go of the gas pedal when I didn't. It will feel like it wants to stall or if there is no power at all but only does it randomly. A new symptom that recently appeared a week ago is that the car started running at higher RPMs or accelerated as I can feel it. It's automatic so no tachometer but I can feel the car running higher than normal. Another recent symptom is that the car will struggle to accelerate from stop, runs okay at 40 MPH, but won't go past 75 randomly sometimes. Things I've replaced: air filter, fuel filter, spark plugs, spark plug cables, coil, distributor cap and rotor, air idle control valve, throttle position sensor, all sensor pertaining to temperature from radiator, new radiator, new head gasket, PVC valve, and MAF sensor. Possible ideas: I've been told include catalytic converter and fuel pump starting to fail. Any help is greatly appreciated as I keep changing parts and no solution just yet. I might end up with everything new on the car by the time I figure this, haha. Next thing that I plan to change is the fuel pump, but can someone help me determine if it could be the fuel pump. Thank you again and God Bless You."

The solution after replacing the fuel pump and adjusting the timing with still no success was to put chevron high octane gas, I must have put 55 dollars to fill the tank, but I was glad to see that as I drove the car on the freeway a sudden bang or small explosion was felt on the car exhaust almost as if something came lose or opened up. I also felt it on the gas pedal as it just kicked into high gear and accelerated well. The car is now driving better than ever with no problems at all. It will accelerate like never before and reach speeds past 75mph easily. Hope this helps and God Bless You.