Following a recent clutch & slave cylinder change I noticed on start up and whilst driving a difference in engine sound (to my untrained ear - somewhat similar to a racing engine). Normally the engine sound was minimal whilest driving. I had the engine tested with a smoke detector - no escapes and all appears normal. Only conclusion reached 'could be the turbo'. A very mature lady driver, I am mystified by the workings of the engine but I do know when something isn't right with it. Can anyone suggest what steps to take next please as I really enjoy driving, especially long distances - I'm worried about breaking down.