Q: garage says exaust ,exaust people says it isnt. any ideas
A: IF IF IF it is the exhaust, it will be rattling against ARCHED FRAME CROSSMEMBER that is directly above the exhaust pipe.. When the exhaust pipe curves UNDER the floor of the car, that's the only metal it could be touching. Put some small blocks of wood, wedged in tight, and race around the block. (just kidding, drive prudently). See if the wood prevents rattling?? UNDER the car, you would hear the location is NOT the engine, and you would suspect the exhaust pipe with more certainty. The first answerer here has a good idea, suggesting the timing advance. IF your car were a petrol model, instead of deisel, I might agree. I have little knowlege about diesel timing, vacuum advances, retarding....sorry. But I don't think the two fuels react the same.