ive got a misfire on my erst estate,it was running 18psi when i had the engine in my s2 erst then it stated playing up when i swapped it into the estate,ive turned the boost down 2 13psi now and it misfires a bit in 1st and 2nd a little bit but not so much or atall in the other gears,i was thinking it might be fuelling problems but its using a bit of water aswell now so could that add 2 the problem if the head gaskets gone