1989 300TE / M103 with 400K+ miles starts & runs perfect but after a while starts losing power under load; will rev fine and you could drive it home by using lower gears. Initially a year ago it would start losing power after maybe a half an hour; as of this weekend it was within 5 minutes! I pulled it into the garage assuming I could spot something but there were no obvious loose wires etc. Went to back it out and it spun over with some almost backfiring but refused to start. You would swear it had jumped timing...... but it had a new chain, tensioner and guides a few years back - no way. Finally coasted it out for the night. Next morning I go out to it and it starts right up and runs perfect so I park it well out of the way. Over the time this condition had been progressively getting worse I have replaced the cap, rotor and wires with new (REALLY needed it), swapped out the coil and the ICM with used parts (no change) and finally last weekend the fuel pump with a new Bosch (@ 400K miles it is probably due?) just prior to the final test drive. Do the cam / crank sensors fail in a heat related manner? Sure seems electrical in nature. We own 2 SLK's (1 manual / 1 auto), a '90 560SEL, '74 450SLC and a '67 230S 4-speed manual. The wagon is by far our highest mile car and the dogs will never allow us to get rid of it. Any thoughts would be appreciated; I've been doing all my own 'Benz work for 40+ years and have not come across this one; until now!