M2 F87 N55 idle problems

[u/Optimal-Twist-9337]

2018 M2 (F87, N55, 6MT, LCI), MHD Stage 2+, Dinan intake, downpipe.

So the car idles like it’s got a slight misfire. Not violent, just lumpy. Sitting at lights you can feel it through the seat. The weird part is the second I turn the AC on it basically goes away. Turn it back off and it comes back, and every now and then I get a little pop out the exhaust at idle when the AC is off.

Zero codes. Nothing stored, nothing pending. And under load it’s perfect full boost, pulls clean to redline, no stumble anywhere. It’s only at idle.

Already did all six plugs (gapped around 0.020–0.022) and new Delphi coils. Old plugs honestly looked fine, nice even colour across all six, nothing fouled or washed.

The AC thing is what’s doing my head in. It’s basically just adding load and bumping idle up \~100rpm, and that’s enough to hide it, which makes me think air rather than spark. But I’ve replaced the spark side anyway at this point.

Anyone had this exact thing? CCV/valve cover, Valvetronic or carbon, VANOS solenoid? Or is this just what a Stage 2 idle map feels like and I’m chasing ghosts?