A misfire — P0300 (random) or P0301–P0304 (cylinder-specific) — has a short list of causes on a GTI, and the code plus a swap test finds it fast. My order is: ignition (coil/plug), then fuel (injector), then mechanical (compression), then the lean/boost story. I don't shotgun parts — I read the per-cylinder misfire counters in VCDS Basics first
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