So I recently bought a 340 1.4 turbo and she fumes Very very badly. On speaking to the previous owner he tells me that no work was done to the bottem end from standard so would lead me to believe that this would be the cause of the problem more specifically the piston rings. so if I installed the Renault 5 gt turbo pistons and rings would this solve the issue ? Would I need gt turbo liners as well ? Any help with these engines I could get would be brilliant as they are all new to me cheers Jamie

I have no experience with these engines but could the turbo seals be leaking?

the turbo isn't very old but it's another possibility and it's fuming out the engine breather like mad not just the exhaust

Have you done a compression test?