cheers all, I've searched on this topic and haven't found anyone that has posted the exact (or close to) my problem. I'm not a wrench-head so I'll try to give you as much info as I can. I have a 2000 Electraglide - with a carburator. In 2008 I had louder pipes installed and the carburator was re-jetted to match the new pipes. Since then, about twice a summer (NY, can only ride 6 months a year), I have this problem: I fire up my bike, it starts fine and it idles fine. I put it in first gear and take off. The engine will start missing, popping, sputtering, coughing, wheezing, etc... It is hard to keep it running. If I can power through these spells and keep the bike running, they last for about two to five minutes. Then, the bike settles in and runs fine. This never happened before I had the new pipes installed. I've also noticed that when these spells start to happen, the engine will pop or miss, once or twice on a ride. The next time it will happen more often, and then I get into the full blown missing, popping, sputtering, coughing, wheezing, etc... sessions. It gets worse with each ride. I've had the bike looked at and the carburator re-jetted again, the carburator cleaned, and new plugs installed. Then it runs fine for a few months and repeats. I've getting tired of paying Harley mechanics for fixes that do not last. As I noted, this only seems to happen about twice a year; the beginning and the end of the riding season for me. April to October. I'm wondering if colder air affects this? Could it be the jets are not operating correctly in cooler weather? I was told when I bought the bike to run high octane gas in it ( 93 grade ). I was recently told not to do this and to run 87 octane. Does this matter? Another mechanic mentioned the Ethanol, which is now in most gasolines, might be causing these problems. But again, only about twice a riding season. With this current session, a mechanic suggested adding a bit of Dry-gas to the tank. I've done that but it hasn't helped. I have a friend who has the same problems only worse. He owns a sportster. I'm thinking there must be others out there with this problem and hopefully there is a common fix. Any ideas or thoughts would be appreciated. Thanks for reading this and for your ideas.