Three months is rough but I get it. Mine was the humidity in my kitchen, not the grinder. Once I started weighing beans first and letting them sit for like 5 minutes before grinding, the static dropped way down. Also try grinding a tiny bit coarser if you can. Fine grounds plus dry air equals everything stuck to the chute. What finally fixed it for me was just wiping the burr area with a barely damp cloth once a week. Sounds dumb but it worked.

Wait, how did you figure out it was that line? Did you just start pulling hoses one by one or did someone on a forum point you there? I'm asking because I've got a 94 GSR with the same rough idle and I keep throwing parts at it like an idiot. Also how the hell do you put a vacuum line on backwards, isn't it just a tube? Unless there's a check valve in it, then yeah I get it. Just trying to learn from your pain before I burn my own weekend.

A $95 labor quote for a five minute dust cleaning is wild to me. That shop had to know the fan was just clogged, not dead, and still charged you like it needed a full teardown. I opened up my old Dell a few years back and pulled out what looked like a felt blanket of dust and pet hair, it was nasty. After a quick brush and some canned air it spun like new and never made that grinding sound again. Shops make way more money selling you a new part than spending ten minutes cleaning the old one.