'86 560SL - weird hot start issue!

[rgnprof]

I have developed a new problem with my 560...cold start is fine, fires right up with no problems, but when I try to start the car after it has sat for 30 - 60 minutes - give or take - the car will start ok but idles unevenly and roughly for several minutes. If I press on the gas pedal, it will stall out...

If I let it run at this rough idle for a minute or 2, it will eventually run fine.

Also, there is a very noticeable "rumbling" sound from the gas tank when it does this - almost like the fuel is boiling...

Ryan