The engine issues were result of the low octane fuel. Performance engines require high octane fuel to avoid "knocking" (or pre-detonation of fuel). The 92/93 oc

The engine issues were result of the low octane fuel. Performance engines require high octane fuel to avoid "knocking" (or pre-detonation of fuel). The 92/93 octane recommended for stock performance engines is not available everywhere, let alone Ethanol blends and 95+ octane required for tuned engines. > Almost guaranteed this thing had a hacked up EFI modification done by some tuner... those guys never really know what they're doing, AMG/Mercedes almost certainly won't share how that computer works since modifying it on a street car almost certainly is illegal and will cause the car to fail inspection. You sure as hell don't know what you're talking about either, because most of the tunes don't touch the software as much as they change "maps" or the data tables that the ECU uses for fueling/AFR, ignition timing, cam profile (VANOS/VVT/VVL etc.). The tunes themselves don't result in a failed inspection (I own a tuned BMW N54 motor myself, that passes inspection without any hacks) but if you're generating enough boost, it may be necessary to remove the catalytic converters in the downpipes after turbos for a smoother flow which results in a failed inspection. Most modern inspections rely on the ECU to report a failed/missing catalytic converter so getting around the inspection is an easy task for someone inclined to remove downpipe cats.