[workingonit]

Thanks, no compression on cylinder 2. The pin/screw that holds the disa valve got loose and made its way to cylinder 2. Upon borescope check, piston got destroyed.

One of the first things I did to my '01 X5 3.0i (M54B30) when I was going thru it (at 20 years old, it was still new to me, though the previous owner had spent 3.5 years practically rebuilding it prior to trading it to me, for my retired dragrace Chevelle), was to rebuild/upgrade the DISA valve.

I had read about the possibility of the pin coming loose, as it did on yours, and took preemptive action to prevent that from happening (I also previously replaced the viscous clutch fan with a high-flow electric aftermarket puller fan, since it was howling and the blades were delaminating...I try to anticipate parts failures).

The G.A.S. upgrade kit was easy to install, and though the original pin was still pretty tight, I greatly prefer the long titanium screw that holds the upgraded flap in place.

The aftermarket puller fan required some ******* engineering on my part to work as I wished (it's thermostatically or manually turned-on, and time/voltage turned-off, with home-fabricated mounting brackets, etc.), but it also gives me a similar assurance of reliability as the DISA kit does.

DISA Repair and Upgrade Kit: GAS BMW M54 3.0L DISA Repair and Upgrade Kit | German Auto Solutions
and

16-INCH FLEX-WAVE® LOBOY ELECTRIC FAN (PULLER)
https://flex-a-lite.com/16-inch-flex-wavetm-loboy-electric-fan-puller.html