Need Help Figuring What's going on with my engine- '97 Nissan P/U???

[ALL2soon]

My engine had been experiencing problems with starting for months, it seemed that, at first starting, it would surge constantly in rpm but never able to rev totally up--after warming, when the surge would finally achieve a 3000+ RPM, I could get the truck driving and achieve a smooth RPM. In the fuel system, I have replaced the fuel filter, the FPR, the oxygen sensor, the air flow sensor and just put in a tuned set of fuel injectors this morning.

To go back, my problems with the engine finally got to the point that the surging would occur sporatically all during driving and starting would take 30 to 60 minutes==undrivable. After putting in the injectors this morning, the engine started right up, but had a unusally high idle RPM [1,500, I keep it @ 900] which did not respond to adjustment attempts, while the engine appeared to be running smoothly. When I opened the throttle, right when the engine achieved RPMs right in the vicinity of 3000, it started experiencing revving surges, but the RPM would be knocked back down to about 3000 RPM while I continued to keep the throttle open, only to begin another rev up/knock down cylce....Any thoughts on where to go now??