Hi, I have a 1996 P reg 218 VVC Coupe. I have had the head gasket done on it and ever since it will not rev past 5500rpm. It does not drive like a vvc should. Sometimes when starting it will idle very lumpy and if I rev it up to about 6500 rpm this will clear the idle problem but then it will got back to the problem of not using the full rev range. Any ideas??