Rough sounding at 5k

[nmh5028]

Background:
2001 GS, 18k miles
V&H system with lunchbox and Bob B ignition advanced
22.5/65/147.5 with 2 washers
Valves adjust less than 2000 miles ago


Bike runs great everywhere except for holding 5k RPM. At this point the engine gets rough and I get the occasional pop in the exhaust. I've tried switching the mid jet to 67.5 and it just made the idle and lower end bog. I'm thinking of adding more washers but was just looking for advice before I take anything apart.