Welcome. Sounds like a possible electrical issue. The headlight/horn relay also feeds the vehicle speed sensor (VSS). This relay is in the fuse panel behind the right side cover. I've had these fail, have high internal resistance. Is the headlight bright, is the horn clear and loud? Could also be a bad sensor or corrosion at the 16 pin connector at the speedo. Should be pin #8, Wire #437 green/brown wire ( I think, I'm color blind). Check for corrosion. If it's been sitting I see hard white powder in connectors, that's the corrosion, it causes high resistance in the circuits. Dielectric grease will be your best friend, apply to all connectors. also this may be giving false speed signal to ECM and account for low power. Also, pull fuel lines off where they attach to the fuel tank. There are screens up inside the steel elbows, they may be plugged with varnish from sitting. I'd run Seafoam thru the tank and also if you can pull a vacuum line off while the engine is running, and suck Seafoam into the engine, it'll smoke bad, shut engine off, reattach line, let it sit half hour and fire it back up. This cleans valves and injectors. Good luck.
2008 Vision Tour Premium
candy cobalt blue, Ness twin sucker, Ness big honker exhaust, stage 3 cams, Ness big shot fuel controller, custom LED lighting