Help me diagnose stutter

[a216vcti]

I have a 99 4Runner 4x4 auto w/ cali emissions. It's currently having issues where it will bog and stutter unless I beat on it. If I cruise really slow or don't go above quarter throttle, it seems like it will start to misfire. Also, I was driving around at 55mph @ light throttle today barely on the gas when it was I made a long left sweeping turn and it seems like that provoked the misfire. As soon as I straightened out the wheel, it went away.

It's been doing this for some time now. I replaced the front O2 sensor last week and installed an new OEM MAF on Sunday. Within the past 10k miles, I replaced the following:

Oil and filter
Spark plugs
Wires
Pcv
Trans - replaced trans with federal junk yard trans. Supposed to have had 90k. Had new fluid and filter installed


It threw a P0171 (lean)and P0172(rich) codes. I recently cleared the codes and the cat test isn't ready. So Even though the codes haven't come back since I changed the maf, I think they will as soon as the cat is ready.it's really strange what's going on. Though, I must say, the car is running better since I changed the MAF. I don't know if there are/were multiple issues.

Anyone know what to do next? I will be doing the fuel filter this weekend but I have little faith that a fuel filter would be so intermittent and cause both lean and rich codes.

 

[fourfive]

If there aren't any pending codes, may be worth taking a look at the coil packs or testing them if you have a multimeter. If the coil packs check out then it sounds like it could be a fuel injector issue. Suggesting this since you already did the MAF & spark plug stuff...

Edit:
-Would also look into cleaning your throttle body if you didn't do that during your maf change.
-Other areas to consider if you don't have any pending codes...throttle or camshaft position sensor