Just thought i'd better mention that you should have non resister plugs fitted(H7 and NOT HR7)
Most if not all suppliers now only supply the resister type plugs(with the R in the title) and even try and insist that they are correct fitment(because they can no longer get the non resister type plugs)
After much searching i found that only the MB dealers could supply me with the correct non resister type plugs. They were only about £1.50 each so no hardship there.
does it make any difference? The car runs great...