Hesitation, lack of power at high end of rpm range

[obadran]

I have a 96 yukon with around 100,000 miles.
Problem 1: Under wide open throttle excelaration, the service engine light would and I would experience lack of power when approaching the high end of the rpm range and would have to back of the gas pedal so that the trany could shift into the next gear. After a couple times of doing this, the service engine light would come on and then after a couple of days of normal driving the light would turn off. I found that I was setting fault codes P0131 and P0151...O2 sensor 1 and 2 high circuit voltage (aka. detecting a lean condition).
Problem 2: On a cold start, back down the driveway, put gear in Drive and step on the gas (not wide open throttle) and the truck would hesitate, lay off the gas and then hit the gas...the hesitation would go away. Tried this again on another cold start, stepped on the gas and kept it there, truck would hesistate trying to gain speed, I think I heard the truck backfiring.

Took the truck to the dealer. They found "stuff" floating in my gas tank... paid for a complete fuel system cleaning/flush.

Now...accelaration is a lot better but still having problems.
Problem 3: Fully warmed engine, at a stop light, light turned green..shoved the gas pedal to the floor (A/C was on). Got to about 4000 rpm and then it started to hesistate and it took a while to get to about 5000 rpm. The trany shifted into 2nd gear....service engine light came on flashing (missfire detected) and then stayed on steady. Read the codes and P0300 (missfire, multiple cylinders). P0131 and 151 were also present but I'm not sure if they were history codes as I'm not sure if the dealer cleared the codes when I got the fuel system cleaned. I also don't know if the tech followed the diagnostic chart for the 131 and 151 codes.

Looking at the freeze frame data for P0300, everything seemed to be in normal limits. Finally to the real question.....

I'm kindof thinking about a bad MAF sensor. The shop manual in one section states the max MAF value to be around 125 g/s at wide open throttle, yet in another section is states at wide open throttle the MAF could read greater than 100 g/s. The freeze frame data says the MAF was at 197 g/s. Is 197 a valid value??
Some other freeze frame data:
LT Fuel trim 1 = 6.3
ST Fuel trim 1 = 0.0
LT Fuel trim 2 = 6.3
ST Fuel trim 2 = 0.0
Fuel sys 1 - Open loop
Fuel sys 2 - Open loop
RPM aprox 4700
engine load aprox 96%

I'm almost tempted to relpace the MAF sensor and see what happens, but not when this sensor is over $200. Could this also truly be a case where both my O2 sensors are bad?

Sorry for the realllllly loooooong post, but I'm getting a little frustrated with the dealer and thinking about switching. But a $90 a pop to take the truck and having it looked at adds up quickly.

Any help would greatly be appreciated.
Thanks,
Omar

[TweakedGM]

just try cleaning your maf first. mine was acting funny cleaned it works better I also changed the plugs, cap and rotor , check your timing to just in case of chain stetch.

[berkes454]

i dont think it could be the timing because then it woul be happining at all rpm ranges, if u clean the sensor and still have problems, have your cat converter checked maybe its starting to get clogged

[ProjectXC]

i had that problem on my 95', i replaced the fuel filter and it worked great after...

[obadran]

If the cat converter was clogging up, would there be any other symptoms?

[berkes454]

weel there are a few, like............loss of power at all rpm ranges, lots of hesitation, weird exhaust note, and and engine light on cars that have them, my best advice to you is to go to a dealership or automovive repair place and have them hook up a "Scope" to your car and they could tell you whats wrong, AND HAVE THEM ONLY DO THAT.

[travis16_93]

i have a 1996 silverado with the 350 vortec and its doing just bout the same exact thing. when its cold and u give it gas, it seems like it takes a second or 2for it to go. when u push it down hard and it gets to 4000rpm it seems like it losses ALOT OF POWER and it also does the same thing in 2nd gear. my service engine light is on but ive not gotit checked out yet.

[yukondenali67]

I Agree clean your MAF sensor and replace 02 sensors
But before replacing 02's beat the crap out of your
Catalatic converter that will un-clog it not to mention
You will feel better. Then start vehicle!1. Clean MAF 2. BEAT CAT CONVERTER
3.REPLACE 02 SENSORS Post your results