My 2000 Ultra has 53,000 miles. The motor, cams, etc. have been taken care of. I've found that it's running rich as my plugs are eventually getting powdery black. At low RPM (cruising like 35mph) it sputters a little or misses briefly. It only happens intermittently. I'm wondering if it's more likely to be fouled plugs or if it might be problems with the old ignition that's on this year. I can provide a list of upgrades if it's necessary. Thanks for any input.