Hello all, I have a '98 R1100GS with 67K miles on it. Over the past month, I've noticed a "stumble" at low-mid throttle openings. I'm having a hard time describing it: stumbles off idle and enters a big dead zone with no acceleration(like a carb jet feels when it's clogged). Cracking the throttle more will eventually fix it as the RPM increases. During this stumble, the bike sounds as if it's running on one cylinder and has increased vibrations. I've noticed this issue both when the bike is cold and hot and through all gears. Lately, I've noticed some pinging or popping on deceleration with a closed throttle. I typically wear earplugs and have only recently noted this so it may or may not be related. What I've done so far: Fuel: I've run multiple tanks of good quality gas of different grades through it. 89-95 octane doesn't change anything. I've also treated the gas with HEET with no effect. Valves: adjusted. Throttle bodies: synced. Spark plugs: replaced and correctly gapped. Air filter: cleaned, no rodent debris in airbox. More ideas: Could the TBs have a vacuum leak and need a rebuild? HES going bad? Coil going bad? Plug wires? Thanks everyone!