I had a similar problem but to a porsche boxster I use to have. was a 98 with only 8k miles. it only sat in the garage most of the time and when ever I would take it out, Problems Problems. I finally took it into the porsche dealer and it turns out a rabbit was living in my engine compartment which chewed some wires up and left some food over near some very sensitve wiring. I got that fixed and the car ran perfect again. Thank god I didnt pay for that. Was covered under warranty but If I did pay, It would of costed me $2300!!!!!!