Great idea to look for the low-hanging fruit before climbing high up into that Tree of Repairs!Just removed as much fuel as possible, & was prepping to drop tank & remembered to double check my vacuum gauge before I do anything & sure enough the needle stayed up at approx 10lbs., even after opening suction line to see if gauge drops.(still stuck) I tapped a little on gauge but no difference. I then popped open rubber seal on top of oil filled gauge and needle dropped. poured fuel back in tank & started engine, & showed approx 2# of vacuum. Shut off engine & needle returned to peg/pin at 0. I'm happy not to drop tank!