1991 Nissan maxima V6 Auto. been having this issue for a while now and keep trying to fix the possible issues and nothing is helping at all. the car starts right up no issues, but idles a little rough like a miss. give it any throttle while driving and it has no power and sounds like a miss, slow as *****. BUT one rps get around 3K the engine instantly smooths out and pulls like a dream. then it will shift and rpm drops below 3K and runs like crap again. been trying to figure this out for months. here is a list of parts rerplaced: plugs, plug wires, rotor, rotor cap, coil, ignition control module, O2 sensor, MAF sensor, cleaned IAC and EGR. I dont believe it is a fuel issue since it runs great at WOT above 3K. I checked for vacuum leaks with Ether and no jump in rpms. the check engine light doesnt come on, but the computer shows a code 33 for the O2 sensor but it is new. seems at almost any throttle position above 3K it runs great, anything under 3K (even WOT) it runs like crap. I am running out of options.....

Have you tried testing resistance on all 6 injectors to see if they're within spec. 10-14ohm?

I have not checked all injectors, but I have taken a stethoscope to them and heard them all clicking away as they should.

Try taking a multi meter just to see if they are between 10-14ohm. Sounds like otherwise you've covered a fair bit of ground. Also i noticed no mention of the TPS you could also try testing it as per the FSM and if you are getting a code for the o2 maybe try checking the circuit as it may not necessarily be the sensor itself. I've heard if the o2 gets dropped it can be affected too.

Ok, yea TPS was my next thing to try. I will check the injector resistance.

Bad injector. That's how mine acted. Replaced fuel injector, good as new.

yup, 2 bad injectors, runs like a champ now.

I had a feeling that was your issue. I take it you did test the resistance on the injectors? What i did after taking everything apart on more than one occation i finally just decided to swap my lower intake and fuel rail to the 94 style which has much better connectors and went with a new set of 6 injectors and just did everything one time. Glad to hear everything worked out and your max is now running well.