I have a 1997 GMC YUKON that has serious hesitation while accelerating, I have replaced the fuel pump and fuel filter, and has not helped, You advised that a Maf sensor might have to be replaced and dirty injectors may have to br cleaned. Where is the MAF sensor located and how or with what should the injectors be cleaned with

SOURCE: Yukon Denali Fuel Trim bank One and Two running too lean?

Could also be fuel filter, pressure, vacuum leak, etc. Check these two articles out, they should help too - http://www.obd-codes.com/p0171 and http://www.obd-codes.com/p0174

SOURCE: MAF Sensor and 02 Sensor

Replace the fuel pump with another one.
This is a common issue.
Don't use an "aftermarket" pump; buy one from Chevy.
I just had this exact same issue in my shop. The truck would run for a bit, and then just stop. I had the truck towed in, and the fuel pressure was good. Drove it for a while, with the gauge hooked up and taped to the windshield, I could see the fuel pressure start to drop off. I told the owner that she needed a new fuel pump.
The owner told me that the pump was 2 months old. I went ahead and changed it anyway. A new fuel pump cured the problem.

Testing the MAF and the O2s is not going to tell you anything. A failure, an open or a short would set the check engine light.
Please feel free to get back to me if you desire any further input. Thanks for choosing FixYa for assistance.

SOURCE: 2000 Gmc Yukon Denali wont start i changed fuel pump and filter

your getting too much air in chamber on igintion probly cause by a faulty intake and or a faulty tps (throttle positioning sensor) sounds like intake is sucking more air that fuel which is giving a bad air fuel mix in chamber also try checking your mass air could be faulty as well

SOURCE: 2002 GMC Yukon, erratic idle(hi-low) when cold. 125K miles.

i now for a fact that it is the egr valve . carbon balls in side you have to take it of and clean them out

SOURCE: my son's gmc 4.3l hesitates upon acceleration. I

do you have any check engine lights on? If you do, that is the first thing I would have checked. It does sound like plugged EGR, vacuum leak, or bad TPS