I have a 2007 GL500, as you drive at above 100kmph the engine check light comes on & the vehicle starts to shake especially at low speed, the mech diagnozed and found cylinder 8 is missfiring. Both coil, spark plug & injector were replace consecutively but the issue remain unresolved. The mechanic suggested to replace the ECM unit but before that I want to check if this is the only solution to resolve the issue?. Once i stop the engine and restart the vehicle the ECL is off & the engine runs smoothly again until it crosses 100kmph the problem occurs again.