Had 2006 car since new and and at point of sending it to crusher but tragedy as tickover problem aside everything is as new. No 6 misfires on tickover but fine as soon as higher revs. Garage exhausted mechanical - new plugs, coil packs (swapped new to try to migrate problem). Timing chains and compression test and piston leak test all good. Second garage suggesting ECU or engine bay wiring fault. Any suggestions?