Was it blocked up?

When it had its mot I got an advisory saying slight oil leak on the turbo. I'm thinking that might be contributing?

I shall check the EGR valve before attacking the turbo I think!

Did it bring the management light on? Mine says "boost out of regulation" or something like that.

Seriously pissing me off TBH. Smoke is embarrasing and I have to drive like a grandad to stop it going into gimp mode. And any road over 60mph is a no no.