My 2001/W203 C Coupe 220CDi has developed a fault where part way through a journey it loses power. Happens after 30mins/30 miles, car will accelerate up to 70mph on flat - on hills it slows to 55mph. Only first 30% of accelerator travel has any effect, the next 30-100% makes no difference. Fuel consumption is also worse, c. 37mpg instead of usual 44mpg. On journey home (8 hours later), all is fine for the about 30mins/30miles and the fault reappears. This repeats every day. There are no fault lights/malfunctions reported on the dash. Spoke with an inde MB who through it was the MAF. They said stop the car, remove the key, wait a mintue and any fault code would be cleared and the car would be OK. Tried this, but the fault was still there immediately I drove off again. Any thoughts ?