Guys, I have a GTV with the 2.0JTS engine. I've noticed that after a "brisk" run on the motorway the back of the car above the exhaust pipe has a thin layer of black sooty stuff. Has anyone with the same engine in a 156 experienced this. I took the plugs out at the weekend and they were pretty back and sooty ( cars done 4.5k miles).
Hmm, doesn`t sound quite right does it and the sooty plugs are a bit of a giveaway. As a suggestion, try a 50 mile run on the motorway if you can, without any hard acceleration - just keep the throttle light. If you still have the problem with bodywork and plugs then it sound like it running too rich (you may notice poor fuel consumption too). It could be that the engine management thinks that the engine is cold and needs extra fuel which points to a (water temp?) faulty sensor.
Alternatively your right foot is too heavy
PS he said above the exaust, not the exaust itself guys. Everyone gets black exausts - must be that alfa owners heavy foot again.