Bad experience with a "German car specialist", need a second opinion

[brandonhill]

Took my Tiguan to a garage near Al Qusais that advertises itself as a German car expert because my check engine light came on and the car was idling rough. They kept it for two days, replaced the spark plugs and ignition coils, charged me just under 2000 dirhams, and the light was back within a week. When I called them out on it they said it's probably a fuel quality issue and to use premium petrol. That explanation felt lazy, so now I'm looking for a second opinion before I waste more money. I've seen a place advertising premium Volkswagen repair near Al Qusais and I'm considering booking a diagnostic with them just to get a proper read on what's actually going on. My worry is that whoever I go to next will find the same thing, want to charge me again, and I'll be stuck in this loop of paying for guesses. Has anyone here dealt with persistent misfire codes on a TSI engine and actually gotten it sorted properly? Would really appreciate hearing what the real cause turned out to be.