So, it's missing and drops 100-150 rpms even when warmed up. (Don't just replace everything you think might be the problem. Diagnose the real problem and fix that.)

Could be the #4 injector. (there are places that rebuild/repair/remanufactor injectors and match the calibration for all injectors)

But, the engine is controlled by the car's computer and the computer expects the info from the sensors to be real/true.

What happens if a sensor malfunctions, the wiring connecting a sensor to the cpu opens/shorts intermittantly, or the ground connection to a sensor intermittantly goes out?

Answer: the cpu gets garbage and acts on it causing all kinds of gremlins.