bimmerlife harness and modified R8 coils installed. Everything was looking good on V12 low boost map, but then when I went back to higher boost V11 cyl 4 kept misfiring on the old .016 gapped 97968 plugs. So I installed new .018 gapped 97968 plugs, but still keep misfiring on cyl 4. I tried swapping coils and harness connectors, but still kept misfiring on cyl 4. Should I get some 97506 plugs and gap them the same and try? Or run a tank of techron cleaner through? I'm running out of ideas.