My '92 Vulcan began running rough a few days ago. It starts fine and runs fine for about a mile but then begins to shudder at idle and low rpms. Also runs fine at wide open throttle. Replaced the fuel filter tonight and didn't help. The fuel pump has been making noise for a while now when the tank is around 1/4 full and below, thinking this may be the problem. Any suggestions are greatly appreciated. Thanks!