Rough Idle/Intermittent Parking Brake Indicator

[chugbug]

I'm stumped.

I recently converted my 94 5.7L Silverado from TBI to Eldebrock MPFI (TBI air intake), Vortec heads, roller cam and headers. Truck runs great except for 2 problems.

1. The parking brake panel light flashes on intermittently, varying in brightness and seemingly related to the engine idle speed (brighter when very low (~200 rpm)).

2. At idle it seems to be 'hunting' for an idle speed to the point of almost stalling, 200-1000 rpm.

I have checked the DTCs and none appear. I have interrogated the PCM inputs on rows A, B, E, and F and no abnormal values are indicated except oxygen sensor varies from 0V when revving or at full throttle to oscillatign between .1 and .9V at idle. Is this normal?

MAP sensor is right on. I have checked the grounds, to the motor (Strap on pass. rear) and the 2 wires by the thermostat. Is there a ground to the PCM. Vaccuum is 20 psi off the TBI MAP solenoid connection. Changed thermostat to 195F.

 

Thanks in advance for your advice.