Probably harmless using OE spec plugs with a tune (but I don't/won't). Assuming one isn't driving it hard. The KS will tell the ECU to dial back the timing, but that's no fun. If summers are mild and winters severe may stick with OE plugs. And keep an eye on them.

Not a fan of how NGK's always leak past the ceramic insulator. Seen coil packs partly melted. Can only surmise VAG sourced NGK due to costing in the late 90's.

Have only used German made Bosch FR 5 DTC's in mine. Cheap and readily available. Porsche Air cooled application. Threads are rolled better, so less chance of seizing. I use copper antiseize, but some OEM's specify not to use any. Stuck plugs....are bad, mmm-kay?

Have seen a few cars this season with odd running or mild misfires. No DTC's. Was failing COP's. Plugs showed it. Installed the R8 COP's but not a fan of how the B2 (front left) PCV check valve gets in the way. Then the front carbon cover won't sit right. But seems to run great. Think I'll stick with OE COP's on mine.

Been using copper and silver plugs on my other built turbo car for 25+ yrs. Turbo's are fickle when it comes to plugs.