On my '92 SSE */c, if the engine is warm and I shut off the engine to stop at a store for a few minutes, for example, the engine runs a bit rough for several minutes after I restart it. When it'* running rough, the idle rpms are stable and appear normal, but the boost gage jumps around a little bit more than normal (maybe 3/16" or so as opposed to 1/8" or so normally). After driving for a few minutes, the problem goes away and the boost gage fluctuations return to normal.

There are no error codes, and no other known symptoms.
I haven't used a scan tool to look at the measurements while the problem is occurring, but even if I did, I suspect that I wouldn't see any odd readings.
I doubt that the problem is heat related because it only happens after restarting when the engine is hot; it doesn't happen after starting the engine (cold) and driving while the engine is hot.

I'm wondering if maybe it'* the IAC sensor?

Have any of you encountered this before?
Thanks.

Pull the vac line off the FPR and smell it for fuel. Pooled fuel in the LIM can cause your symptoms.

A leaky injector can do the same. Does it hold fuel pressure after shutdown?

EGR leaks can change with tempurature as the metal expands and contracts.

I checked the FPR several months ago, but I'll check it again.
Roughly how long after shutdown should it hold pressure? About a year ago, I replaced all fuel injectors with a used set that had 30,000 miles on them. Does a leaky injector take several minutes to builup normal pressure again?
I know that there are a couple of cracks in the exhaust manifolds (they've been there since I bought this car in 1999, but this problem just began a few months ago).

Building pressure is of no consequence. A leaky injector will have you running overly rich on startup.

It should hold at least 50% of initial pressure for the first 10-30 minutes after shutdown. Longer is greatly preferred. If it leaks down quicker than that, it could be a leaky injector or FPR.

The age or mileage on your injectors is also incosequential. How long they SAT before re-use is a major concern.

The 97 FSM says they should hold all the pressure for at least 10 minutes. Not sure if your year is the same. At 50% pressure though...you are leaking down somewhere.

I pulled the vacuum line from the FPR and didn't see or smell any fuel.
The fuel rail held pressure for 10 minutes after the engine was turned off.
What should be checked next?

What is your fuel pressure peaking at?

When was the last time you cleaned the TB?

What is your fuel pressure when you get the hard-start condition?

Unfortunately, I didn't use a fuel pressure gage because I don't own one, and I haven't yet done any testing while the problem occurs.
After the engine had been shut off for 10 minutes or so, I pressed the release valve and let the fuel squirt into a rag.
I cleaned the throttle body roughly 10,000 miles ago.

We're back to square one. 5psi will squirt fuel into a rag.

My son'* '99 GP had enough pressure to shoot fuel out to the front of the car, but not enough to start it.