I have owned a '91 RS 5 spd with a 305 TBI for a month now and haven't had any engine trouble. I let the car sit for 8 days while out of town and started it up again tonight. Startup seemed normal (about 2-3 secs of cranking before ignition) but began shuddering/dying anytime I let the RPM's drop below about 2000. The tach arm would start swinging wildly, then RPMs would drop to 0 and engine would die. I could easily start the car up again, but would need to gas it almost instantly to keep it running. From what I saw of the gauges, everything seemed normal.

I drove home 45 minutes at night in the rain with several engine shut outs in the middle of turns due to low RPMs and had to strong-arm the steering wheel due to loss of power steering.

The only mods I've done are remove the crankcase vent tube (replaced hose with breather cap), removed THERMAC valve on air intake and plugged its vacuum line going to TBI with rubber cap. This was done 2 weeks ago, with no problems resulting as far as I could tell.

What's up with my baby?