Cuts off while idling

my 89 birds catalytic converter was bad and that caused a good deal of carbon buildup, i had it replaced and the system flushed and the igniters cleaned the mechanic said it was good to go but every now and again it cuts off when iam at a stop and when it starts cutting off it does it multiple times through a period of time then it starts running fine again. its getting annoying so i was wondering does anybody have an idea of whats going on?

Sounds like a ignition issue to me. Or could be a problem with the wiring to your fuel pump but I woud lean towards the ignition. I would put a spark tester on and check it out when it has these issue's.

When it dies, does it just abruptly shut off, or slowly "chugs" to death.

Also, TBI or TPI motor & size?

its a combination, sometimes it chugs out and other times when iam in drive stopped at a light and i take my foot of the brake it abruptly dies out. when iam stopped on a steep grade it cuts off, sometimes when i put it in reverse it dies out. i thought the timing might be off. also iam running sunoco 94 octane through it.

sounds like signs of fuel pump. Is it modded? and what year and motor is it? and how manny miles.

Alright, well you still haven't mentioned anything about the motor specs, but, I am thinking from the relavtive area of where the exhaust runs, I'm wondering if either:

A the 'cleaning' method performed has relocated carbon debris and clogged the injectors or fouled the plugs or O2 sensor,

B the shop that did the exhaust work either hit the wires for the torque converter lock up and it is malfunctioning,

c sent a static shock to the ECM while welding the exhaust back together (rare but happens)

d wasn't paying attention when putting the car on the lift and pinched a fuel line partially shut.

not modded, 89 2.8L F1, 53000 miles, and i dont know all the specific engine specs.

I'd pull a couple of plugs then and explore option A.

Direct rail feed cleanings are great for cleaning the fuel system out, but if the build up was really bad, then when it get's loosened up, it has to go somewhere else and usually not out the tail pipe as intended.