[TinCanSailor]

Have them cut into the oil filter to look for metal flake. Search around the rear diff for fluid leaks, diff brace for cracks as these have a issue with eating themselves under high torque launches.

The turbo coolant lines are a known issue and often end up spilling out in the the upper valley of the engine and is hard to see in there without a borescope camera. The previous owner may have already had this done as they tend to fail in the 50k to 70k mile range.

We have been through this twice on my wife's F10 550. This can also lead to oil leaking down the backside of the engine and down the transmission. There is a weep hole on the back of the engine but is hidden by the transmission housing.

Make sure the door features work soft close, locks etc, not an expensive part but can be time consuming to repair so if you take it to a dealer the cost will smack ya.

Hopefully they have an obd tool that can pull BMW specific codes. Have them look for any stored codes. Misfires might be occurring as the injectors could be the originally installed. BMW does warranty them until 10years/120k miles but will only replace the ones that are failing. I am not sure how they treat tuned cars. If they can check the condition of a couple of the plugs that would help tell the tale.

Turbo rattle can also develop and be much more apparent with catless DP's.

If I can think of other issues I'll drop back in and post em up.