1991 500 SL Engine cuts out

[daubs]

Hi people. I have a fault on my merc 500SL which is:-

From cold engine starts and runs fine until the temperature reaches around 80 deg then when you come off the accelerator (gas) pedal the engine cuts out, if the car is moving fast enough only the rev counter drops and no warning lights come on, then just touch the gas pedal and engine comes back in . However if your travelling slow engine cuts out charging light comes on and you have no power steering and brakes. It will do this 3 to 4 times over a couple of minutes then be fine for the rest of the day. If its started from cold and left ticking over until it reaches running temperature it does not cut out.
It always happens on or around 80 deg and i suspect its the fuel being cut off until the temp rises a little more.

Anyone got any ideas Thanks