I have heard the advice.... tighten it until it breaks and then back off 1/4 turn

No sign of it. I assume it came off while driving as I have done about 1200 miles since I changed the air filter, and the idling problems are recent. It would have dropped between the cylinders, so I would guess it rolled out from there.

When I used to race sailboats, we would sometimes toss a nut or two onto another boat. Would drive the crew crazy trying to find where it went

Rodger, where/what did you race? I'm an offshore, short-handed and distance and guy myself and pull a lot of RC duty in Newport and Long Island Sound.

This was decades ago in the San Francisco area with one design boats. My dad raced Snipes, I started off with an "El Toro" which is an 8' dinghy and then in high school build an OK Dinghy which was a junior Olympic boat a wee bit smaller than a Finn.

For those fitting one of these filters, I recommend taking a close look at the alignment of the filter to the cylinder heads before fitting the chrome mount “arms” that support the air filter. In my case on re-assembling mine having fitted the replacement bolts and O-ring that attach the throttle body to the inlet manifold, it was clear that this alignment was well off. I suspect this was why one of my throttle body mount bolts bolts sheared off (see above) and caused the air leak, as tightening these up before must have put a lot of tension on the throttle bolts.

I tried to follow kankeL’s advice on loosening the intake manifold bolts, but the lower ones are very hard to access and I could not get them loose, so instead I put a couple of bends in the mount to create an offset. It is soft enough steel that it bends easily. See below.

Having finished re-assembly with copious loc-title, it is now idling and running great again. Phew!

When I installed mine I remember something about the offset distances and spacers maybe being involved? I installed and purchased mine in July 2019.

When I installed my Stealth Air Filter one bracket came made with the offset the other not, so they were fitted to the appropriate side!!!

Interesting. Mine were both supplied flat.