[Exxie]

Thanks for the replies guys. The replacement EGR bypass pipe never arrived. The seller tried to claim that he posted it but could provide no evidence. I don't believe he intentionally sent the wrong pipe, but he certainly had no intention of fixing his mistake.

I've now purchased a different one from a different seller (went on holidays for a few weeks), which will hopefully arrive this week. When I install it, I'll also rip off the intake manifold and give it a good clean. If overfuelling is the issue, hopefully this might help. Should I change the gaskets while I'm at it?

Re the thermostats, is it likely to be the main or EGR stat? With the bypass pipe fitted, do I even need to worry about the EGR stat? The car does get a little "chuggy" after it's well warmed up, perhaps because it thinks it's cooler than it really is. This isn't the cause of the smoke because it smokes even from cold start, when it's nice and smooth.