Hi there I have a 55plate Mondeo 115bhp diesel and I have same sort of problem, when accelerating there is a big sound of air escaping and black smoke, and the car revs up and down by it's self when it is kept at the same speed like in cruise control (hunting I think someone said), could this be the same problem the boost pipe many thanks Steve p.

Steve p, September 2012

Thanks for answering it's a bit difficult because you can only here it when accelerating, I can't here it when car is stood still and reving it.

Steve p, September 2012

would check out where you are hearing air escape from,check intercoooler/hoses /air intake

cdc, September 2012