2001 QX4 down on power/surging under load/pinging/no codes...help

[sporttour]

Pardon me if this topic is old but here goes. Have a 01 QX4 second owner, bought at 39k miles about a year ago, now have about 60k on the clock. Ever since we bought it it has surged under accelleration just about any rpm bout especially above 3000 rpm when trying to moderately add power without downshifting. It feels like its down about 100 horses when this happens and its happening more frequently. With the cruise set at 65 to 75 mph all is well until climing a grade then the car starts to surge and buck to the point that it downshifts and even then its feels like it is laboring to get any speed up. If you lift your accellerator foot slightly while trying to get max power it actually feels like it pulls harder, then step back in it and it just bogs...lots of intake snarl noise but no poop..! Once the rpm reaches about 4500 to 5000 rpm its finaly starts pulling with at least a little authority. It feels like it is leaning out badly and my wife says she can fhear rattling or pinging coming from the engine... I use only name brand 93 octane fuel and the best oils, the dealer replaced the MAF once and the rear 02 sensors anothe time... I have no codes and no CES lights.... fuel pressure or volume?... carbon?... I did use a K&N filter for awhile but learned my lesson... the oil may have contaminated the current MAF but I have cleaned it with the right stuff... At times when the engine is running right it really pulls hard but most of the time it fells like a dog... help please, I am tired of the dealer driving my car through the parts department.

[sporttour]

Ned, I certainly will... after two MAFs I have my doubts about another but I was using a K&N air filter until recently.... I found a nice little pile of oily dust on the leading edge of the sensor inside the MAF.....cleaned it off and pulled out the K&N thne replaced it with a high quality no-silicone paper air filter.... the Purolator filter is the best I found next to the factroy unit... I believe there may be a fuel delivery rate problem...my fuel filter has been replaced, no change... there a many ways to restrict fuel flow both mechanically and eletcrically..... anyway I need specs.....pressure and deleivery rate from the pump to the fuel rail...... I am going to try and cut this string to the VQ engine forum, maybe there are some real Infinity/Nissan techs there.....