Former 80'* GM dealer mechanic here. I have an 1989 Cadillac Fleetwood Brougham w/a 5.0 Liter 307 CID V8 Oldsmobile Engine Code Y w/a Computer Command Control Rochester Quadrajet Type R-4 Model E4MC Carburetor #17088115 w/a THM-200-4R MW9 Automatic Transmission w/a lock-up torque converter. 120K miles. New fuel pump. Carburetor recently overhauled w/a Echlin TPS, brass float, and methanol-resistant acellerator pump. New Bosch O2 sensor. New Duralast (Wells) MAP sensor. New vacuum hoses. New 195 degree F thermostat. New PCV valve. New Bosch spark plug wires. New Echlin cap, rotor, and coil. Bosch Platinum spark plugs. I'm in the city, driving light to light, stop sign to stop sign, seldom exceeding 30 mph. During the time I'm approaching my next stop I'm coasting, foot off the gas. I begin to apply the brake (whether it be the power brakes or the parking brake) finally coming to a complete stop. The car is now at a complete rest. One to two seconds afterwards, the engine rpm'* suddenly drop, the car almost stalls, followed by a brief but definite shuttering and sputtering to make its way back to a smooth normal idle speed, the car jerking back to life. So badly is the rpm drop that the headlights even go dim. And still no codes are set. It’* like the ignition is cutting off then back on again, a complete loss of power but only for a moment. Plugging off the EGR valve vacuum hose doesn't help. Plugging off the idle load compensator vacuum hose doesn't help. Unplugging the TCC solenoid doesn't help. I thought the issue was motion-related until I jacked up a rear wheel to simulate a driving/stopping environment and found the event continuing to repeat itself. Crazy right? The event truly has to do with the warm engine and transmission returning to a loaded status from an unloaded status (from coasting in Drive 1, 2, 3, & 4 or Reverse to reaching a complete stop). I cannot trigger the event in any other way. Please share any thoughts you have regarding my situation. Thank you. Cris, Ohio USA

i would probably try to see if i could narrow down some of the vacuum problems, maybe plug the ports at the carb and if it still does it spray around the carb base and intake for leaks w/carb cleaner. does it have a dist like a tbi engine? check advance?