Turns out it was low ground idle. My mechanic adjusted the idle speed and mixture and the problem seems to have vanished. Every now and then you get lucky with a cheap fix. Cheers.

It usually occurs between 68 and 85KIAS with MP<6, prop full forward, and mixture rich. I think the engine idles at around 940-960rpm, but I'll go out and confirm that tomorrow. Thanks for the input.

Hello, I'm new to the forum. I'm prepping for a commercial checkride in my 2012 DA40XLS. When performing simulated engine out maneuvers and steep spirals, I'm getting a fairly significant engine vibration and an occasional popping from the exhaust. This happens only with the throttle closed or nearl...