So I just wanted to share something I'm not proud of hoping I can help others avoid this fail. Friday (4/9/21) I decided to do a leak-down test on my BMW track day car. It's a fun car but it's gotten progressively weird acting like a vacuum leak. The MAF basically no longer works. So what I found was not terribly surprising except for the shear volume: roughly 30% leakage!! Damn. I'm surprised it runs at all. That said, it does run with the MAF disconnected (running a default curve). SO found my vacuum leak. Felt like I could run a tube to the rear of the car to get additional speed from the thrust produced by the blow-by. So I buttoned it all up and put my tools away. Next day I go out to start the car. I hear a quick vaguely loud *SNAP* sorta like when you miss a shift. Then it's just running like normal... I'm like huh. What was that? I immediately think, Did I leave something under the hood. I start thinking back to the tools I put away, the stuff I took off and left off... Then I'm like, OH ****! Guess what I forgot?? Yup, totally gapped on the wrench I left on the crank pully! SO the wrench spun around, smacks the water pump pulley clean off. That drops into the radiator and punches a few holes. And it spun the crank pulley bolt out. What a dummy. I've been building/modifying cars and engines for 20 yrs. Never did that before. Guess I gotta get myself a whiteboard to keep track of what tools I've left in the engine bay. Anybody else willing to share a story? Thanks team.