sorry m8 what i meant by comp test was on the water system its a pump you put on the exspansion bottle you pressurise the cooling system and look for a steady drop of it can search out the head gasket this is best done with a warm engine even if it runs like shit get it warm or run it see if it seems to be presureising rock solid top bottom hoses are a clue or run it for coule mins at a time and unscrew the exspansion cap slighty and note if its building presure each time or try a snifer ive never used one when warm if its very steamy out the exhaust but these days you cant really tell by that one my cossies steams like fuk esp in the winter stainless exhaust absorb moisture if its not head gasket or that plug your looking at the feul injection metering unit would be a good place to start if that the case its cheaper to get a specialist to look at that side only take one hours laboure to diagnose sorry for banging on i f...ing love it lol i only said because i didnt make my self clear in the last post