I own an 91 crx si, y7 trans, z6 motor running on pm6 ecu and intake mani, when i first start my car, it idle's around 2000, then drops 1800, 1200, then stops around 850-950, once the car is fully warmed up, and i start driving, the rpms go up as i accelorate. once i push the clutch in, the rpms drop to 0, car still runs, doesnt choke or studder, but need to rev the engine around 2500 to accelorate without bogging down. the boggin is only bad while starting rolling, but rpms drop in any gear.

 

sounds like either your IACV or TPS went bad