My 06 electra glide classsic just started acting up. I have put new plugs in and changed out the gas in the tank but the problem persists. When the bike is started it idles at 800 rpm, which is lower than normal, then i increase from idle to about 1500-2000 rpms itt backfires pops and misses. do not know what is going on. Any good advise would be great thanks