Usually when your vacum booster goes the brake pedal gets hard but there's no stopping effort.
Make sure your one way valve on your booster hasn't gone out.
Also, I would test the IAC wires for proper voltage and the IAC itself....I found this online and though it might help.
Tom wrote at 2008-11-16 2023
I recently had the same problem, every time I took my foot off the gas the RPMs would drop to 0 and then bounce back. If I was driving fast the car would keep running but at slow speeds it would stall, this normally only happened after the car had warmed slightly (the electronic choke was off). My first inclination was to check all vacuum lines for a leak that might be disturbing the air/gas ratio and leaning the mixture out too much. I conducted a visual inspection of all vacuum hoses and found one to be dry rotted (EGR) and another broken (cruise control), no wonder it no longer worked. I performed some simple routine maintenance, replace air filter, pcv and spray clean the throttle body, all to no avail. I repaired both the aforementioned vacuum hoses and still the problem persisted (cruise control works though). Next I began to trouble shoot with parts and the one most mentioned in blogs like this was the IAC (idle air control valve). I removed the old and other then being dirty there was nothing visibly wrong with it. I bought a new one anyway ($49) and installed it. To my chagrin the problem still persisted. Day two; now totally frustrated I decided to take it to the parts store and ask them to read if there were any codes, there weren't. While I was there I bought a $25 vacuum gauge. Once again I pulled the beast into the garage and surrendered to the idea that another day would be wasted. After having removed the air filter and hooked up under hood lighting I began testing manifold vacuum pressure. What I found was a steady 19Hg, even when I removed hoses from the manifold while testing the engine would compensate and the gauge would return to 19Hg, it wasn't until I plugged one of the disconnected holes at the manifold with my thumb, that the car stalled. This made me think that the problem wasn't too much air but not enough and the car was being choked off when the gas was released. I decided to remove the new IAC and reinstall (start over). My OTC repair manual suggested testing the IAC several different ways, voltage, key on engine off movement and increased idle when AC turned on. The new IAC passed the voltage test but failed the movement and increased idle test. It was getting to the point where I was going to start doing things that would hurt, like removing the IAC and starting the car, what a racket that made. I reviewed the instructions that came with the IAC and one paragraph stood out, the length of the plunger+shaft should not be more then 1 1/8" long, the one I held was extended 1 1/4". I screwed the plunger down, all the way down so that it was extended only 1". After I reinstalled it I performed voltage tests on the throttle position sensor and found it was OK. Time for a test drive, without replacing the air filter I took it out. VOILE, no more stalling The only thing I can figure is that either the IAC port hole was clogged and I unclogged it when I rant it uninstalled or the IAC plunger was too long. Both conditions must have been choking the engine off and causing it to stall when the throttle was closed suddenly.
Also I have seen two pots wherein the PCM was replaced. But I'm thinking you have a slow or non responding IAC valve. If it tests bad, buy a new one from the dealer.