Low Idle, Rough Acceleration, Shakes a bit

[duffs396]

93 Silverado, 350 TBI

After replacing the intake manifold gaskets, I've been experiencing a low idle in park, even lower (200 rpms) in drive. Acceleration is poor but eventually when it gets up to cruising speed 40mph+, it doesn't run as bad.

Also, approx 5 mos ago, replaced ign model, plugs, wires, cap, rotor.

I've done the following:
Checked for vacuum leaks everywhere; cigar method, starter fluid, etc.
- REPLACED IAC Valve
- REPLACED PCV
- REPLACED PCV to Carb vac line
- tested EGR vacuum - OK
- tested EGR Solenoid - OK
- tested TPS OK, voltage up/down as throttle is moved (ign on, not engine) - OK
- tested MAP Sensor voltage drops as vacuum (vac pump) is applied (goes from approx 4.7 to 1.9 Volts)

Have set timing to 0* several times with brown/tan wire disconnected. Timing then adjusts itself to about 1/2" off the timing tab.

The last test I did was to completely cover the throttle body with plastic to try and smother it from the top, almost stalled but did not.

I still wonder if I did a good job with the gasket sealer when I replaced the intake manifold gasket.

There's a lot to digest, sorry for the long post but wanted to give as much info as possible.

Thanks,
Duff