I generally run "un-corked" but occasionally put the plug back in for sponsored trail rides, just to run a bit quieter. With the cork back in the pipe, the engine runs at high idle for a minute or so, then slows down to a very low idle. That makes it bit of a pain for tight single track as the faster idle speed is constantly pushing the bike and I clutch way more than if riding in "Un-Corked" mode. Was the factory jetting set up to the uncorked mode? It idles very well when uncorked and returns to its low idle speed as soon as I let off the throttle. Would I need to re-jet to make it run well with the cork in?