Right i have a 2001 s3 bamg engine stage 2 remap, few weeks ago i had white smoke on start up, loosing coolant fluid, juddering slightly on startup and misfiring at higher revs, just had cambelt and water pump done so wasnt that, had two garage hydrocarbon test it and it was leaking exgaust gases into coolant and all pipes were rock solid just after start up, anyway went on and had hesd gasket done and all other gaskets and seals done whilst it was apart, there looked to be no cracka or visible signs of cracking so put it all back together again, now when it starts the idle problems have more or less gone but did the hydrocarbon test again and instantly it detected exhaust gases, so this all point towards a crack in the lower half of the engine my qusstion is could it be something else that could be the result in exhaust gases leaking into the coolant system? Thanks