This has probbably been asked many times before, so forgive me, but can someone offer some advice? I have a E220 cdi (year 2000 model). It smokes badly under hard accelleration. I just had the MOT done and the guy said he had to rev it five times before it passed the emissions test I have changed the oil, changed the air filter. Car starts and runs well, mpg is good. Smoke is black (not blue). It has done 130,000 miles. Any ideas?