[zaxx81]

I just fixed a similar problem on my '83 944. It was having problems intermittenly starting. As many of the other suggested you might check your DME Relay (a.k.a. Fuel Pump Relay). This unit has two relays inside of it. One relay closing when the key is turned to start the engine. This in response closes the other relay which will be closed continuous, while the engine is on. Relays or any electro-mechanical device can be sensitive to temperature. The other relay being on continuous while driving can produce heat in the unit making relays stick. You could experience the same thing with a cold engine, but the weather be nice and hot. Hope it helps some. I got a replacement from a Porsche Dealer for $16. O'reillys and Autozone won't carry them.