My Goldwing is fine when cold but when it warms up, it gets sluggish, erratic idle speeds, blowback in carbs, all when under 3000 RPM. Also backfires when accelerating. Dealer says it is a vacuum leak but they wont work on older GWs. I took covers off on top side but didn't see anything. I love this bike but this is frustrating me. HELP!!!!!