came into workshop with severe misfire. cylinders 2 and 3 had low compression, and headgasket failure detected. new gasket etc fitted. severe misfire gone. however when revving up it splutters at approx 3000 revs and then clears at 3500ish. prior to HGasket customer had changed plugs, so we have not changed. new leads made no difference. 2nd hand working coil pack also made no difference.
any ideas?