Lumina ltz 1998 idle problems

I need help with the problem we are having with our 98 LTZ (Lumina). I drove the car to and from work all week without a problem. My husband started it tonight and heard a "POP" sound followed by a puff of smoke from the engine. Engine immediately died.

I came out and restarted the car. It would only stay running if I had pressure on the gas pedal. Subsequently, after a few times revving the engine, it stayed on by itself but idled up and down almost sputtering. The interior lights fluctuated with the engine. We drove it around the block and while the gas was being pushed it drove alright. Did notice the brake stopped working altogether.. the pedal got stiff and wouldn't be depressed at all.

My question: What is an ICM and does anyone think this could be my problem? If not, what other things could it be?
thank you

Look for a large vacuum leak,,the pop was a possible back fire which could blow off a major vacuum source.

99% is that it's a brake vacuum booster hose. Most probably it came
off the big black round box (the brake booster) sitting on the firewall
on the driver's side under the hood. The sound was created when the
vacuum was filled with air. Just put the hose back and find some
clamp to fix it. Even zip-tie would work for the first time.