Does anybody know the acceptable IPW range on a 99 4.3L?

 

We'll need A LOT more information to be able to answer that question... IPW depends on a lot of different inputs to the PCM. Throttle angle, MAF/MAP, RPM point the PCM to a specific IPW value in a lookup table. This value is then modified by the LTFT and STFT (different for each side of the engine) to give you the final IPW. This value is always changing depending on the sensor values.