I have a 1997 GMC Suburban. There's been a problem with acceleration for about 6 months. Basically, truck start fine, no hesitation. Idles fine. Sitting in park and revving up the motor it sounds fine.
When I'm going low speeds of 20-30 MPH the truck runs fine. but then when I try to accelerate, it sputters and cuts out (never dies) until I release the pedal and then it runs fine again.
When I start the truck, the fuel pump has gotten louder, and now while its running the whining the fuel pump makes kind of goes up and down in pitch. I have replaced the fuel filter, newer plugs, wires, rotor. I took it to Autozone and hooked it up to the code reader and it says it's running lean on bank 1 and bank 2 (engine light is on). Truck has 168,000 miles.

I think it might be the fuel pump, but I have also heard it could be the O2 sensors. I can't afford to replace everything right now so I was going to do the fuel pump myself this weekend but wanted to make sure that was the problem. Has anyone heard of this situation before?

Thanks for any help!!