hello i have a 2003 st 170 yesterday the engine started misfireing and cutting out and would not rev more than 4000 revs,took it to the main dealer who checked plugs leads and coil and its still doing the same now engine management light is on please help
If the check engine light is on you're throwing a code and the dealer should be able to read it and figure out what's going on. If you're dealer can't do that I'd start looking for another dealer.
I was about to suggest going to AutoZone as they'll read that code for you for free, but I see you're in England. Maybe you have an equivalent auto parts store there?