I have a problem with my bike. For no reason a few weeks after I put on a fmf powercore IV with the quiet insert the bike starts acting wierd. It's kind of hard to start now and when it warms up it backfires a lot and won't idle. it just stalls. Before this it was jetted perfectly but by the previous owner. It started on 1-2 kicks and made loads of power! Any idea what happened?