I have replace the knock sensor and the rear O2 my computer is throwing the 0505 code but I still have an erratic pulsating feel when accelerating between 3-4k at 1/2-3/4 throttle. Does anybody have any thoughts on this.

 

Fuel filter. Spark plugs.

 

fuel pump may be going out, or valves could be out of adjustment

 

I did that already not to say that the spark plugs aren't crappy but the fuel filter is fine. And wouldn't spark plugs cause problems at wot also?