hi there i done an engine change on me s2 and the engine was running fine when i took it out the other car now its in mine there is a miss fire when u rev up its gone and when u are driveing slow it there and when u pick up speed its gone the only thing i have not changed is the metering unit cud this be the problem and as my sump gasget is leaking somone said it might be that cud some help me plz