I'm not sure if you can make it out, but I put a 3/16" vacuum cap on there and used a spring clip to hold it in place.  I'm fairly certain I don't have a leak from the vacuum port.

As for the filter, it was cleaned and serviced just last month.  Those spots are from where I used to have it attached directly to the carb, and the top used to hit the seat/tank mount bracket.  The only thing even touching it now is where the wiring harness goes over top of it.  It has LOTS of available air flowing to it.  You should be able to see int he picture, it's pretty free up.  The seat gives it another couple of inches of room up top, too.

Had an evening ride out to dinner with the wife, and I got to hit my reserve!  According to my mileage calculations, reserve was hit right around 2.28-2.3 gal.  traveled about another 10 miles til my fill up, resulting in 2.478 gallons to proper full.  While the remaining fuel did have slightly less of an aft decline, it was still there.  I had no issues travelling at highway speeds up and down hills on my reserve.  For the next few days I'll ride without the fuel filter (which I didn't have time to remove tonight) and look for any change.

Ran into another WEIRD issue that kinda freaked US out.  Different enough that I'm starting a new thread.