2000 xterra misfire maybe?

[s.price0789]

hey guys im back at the ol xterra again "2000-X-xe-4x4-5spd-3.3" now its doing something that i dont really know what to call but basically while im driving my truck it feels like im pulling a trailer, then when i hit about 2500 rpm's, i lose the hypothetical "trailer" and i have more power than ever up to 4000 rpms it has never been like this before i know these arent exactly race cars but i know i shouldnt have to stand on the throttle just to get it moving then be tossed back in the seat lol does anyone have any ideas what this could be? jus a lil catch up - new parts on it are - exhaust, k&n filter, plugs and wires, distributor, cap, rotor, timing kit "timing belt did break at one point" - replaced ALL valves and seals incl complete head set and vac lines. i think that is all for now any tips/suggestions/opinions/knowledge of any kind is GREATLY APPRECIATED!

[PapaSmurf2k3]

Could be a lot of things... if your valve timing is off, you could definitely have MORE power up top, while suffering down low. It'd also be worth taking a look at your TPS and MAF sensors. Definitely post your results! And post some pics of the ol girl!

[s.price0789]

i tested my maf and tps with a voltmeter and a solus scanner both seem fine i suppose it wouldnt hurt to clean the maf im more worried than anything that i didnt do something right when i rebuilt the heads... it was kind of a learning experience lol and ill have to get some pics up i was trying to hold off till i got my lift and new wheels but i want to get her running right before placing that order :p

[PapaSmurf2k3]

Well, you could always try to find someone with a wideband O2 sensor and see if you're running rich/lean at whatever RPM you want. Where are you located?

[s.price0789]

im in saint louis i actually work at a shop out here and unfortunately no one else in the business out here that i know is willing to give me any input or take a look at it i really dont trust any of the shops around me every time ive taken a car in they charge me $200 to look at it then tell me the wrong thing is wrong with it... like last time i my 240sx to a place called the "import specialists" they kept it 4 a week charged me $250 said i needed an ecu wich i soon found out on my own it was the maf... lol anyways back on topic i plugged it into our scanner at work i have 3 02 sensors reading lean and one that bounces between rich and lean at idle.. thought that was a little interesting i was also able to run a power balance test with it shutting off each injector at a time wich told me all were working as they should im really beginning to think i fudged something up when i rebuilt the heads and put it all back together also i was never really sure in my gut that i had it in time right i have all marks lined up and the light shows its good by the manuals standards i guess what i really need to be doing is running a compression test at this point i just really dont know if i want to tackle that tear down again