runs great then bad on 1990 Nissan Pathfinder

1990 4x4 pathfinder, v6 5speed
problem: runs great up to 3500 rpms all gears but once over 3500rpms starts banging out, already replaced cap, rotor, and fuel filter. Distributor shaft doesnt have any play as i was told to check this because its a common problem.computer flashes code 55--ECCS normal
any suggestions?
Thanks

1 answer 3 comments
Do a back pressure check on your Catalytic converter, it may be plugged. 3500 is the point where a plugged Cat will give you problems. I assume timing is right on the money as well as the timing belt setting, yes? It did not slip did it? A slipped belt can/will cause this type of head ache. I have dealt with it before on a Nissan.
Checking the timeing monday after work...sounds good by ear but havent put a light on it yet..just seems to be starting and running to good to have jumped timing!! but thats 1st on the list and then the cat pressure check and I'm hopeing to let you know which one fixes the problem!! Thanks for the info
This sounds alot like the problems I had when they started. The banging and bucking eventually worsened. After replacing plugs, wires, caps, filters, sensors, I replaced the entire distributor Fixed it right up
That is exactly what is happening to my 1990 pathfinder 4x4. I'm hoping to changde the timing belt soon. I think it jumped a couple notches when I did the plugs and wires due to an old belt. I've also been told an ignition (timing) key, inside where the belt is, needs to be replaced.?