Car starts and runs fine when cold.

Car runs fine when warm.

When first started while still warm starts normally but "hunts" while idling, idles rough and accelerates VERY,VERY slowly, feels like no fuel pressure. Within about one minute or so it suddenly recovers and runs fine until shut off again.

If I open hood to listen for air leaks, wiggle connections, etc it will idle roughly for a minute or so then suddenly revert to running normally.

My guess is it might be the pressure relief valve, but seems odd that it would be so consistent. Tried tapping on it, and removing vacuum hose while idling rough to no effect.

Also thought it may be some temperature sensor, but doesn't seem like rich mixture (no black smoke, etc.)

Checked and cleaned the contacts on the fuel injection relay (no solder joints to fail)

No codes set.

Hard to diagnose because doesn't last more than a minute or so.

Any ideas will be greatly appreciated.

Let it run for a little while with the vacuum line off of the FPR. I had similar problems with my 91 940 SE Turbo. Drove me nuts for a while. I would pull the vacuum line off of the FPR, no difference... but once I forgot to put the hose back on, and the FPR started to trickle a small stream of gas. Replaced the FPR, and the problems went away? Luckily I had a spare to install.