There are a heck of a lot of valves seals on a 32 valve engine.If your machine shop damaged any of the exhaust seals while putting [pound] them on then oil can run down the guide while running and the oil doesn't go into the combustion chamber but right into the hot exhaust header.So you look at plugs and they look fine because the oil wasn't burned in the combustion process.Engine runs fine because oil is not effecting combustion.The only thing is that when the car sits after it is hot I think it would smoke on start up.How bad where the valves bent when the belt tore?Did they replace the valve guides? Where any pistons damaged?I have seen some really screwed up valve jobs by people that are not used to working on stuff like the Audi V8.
