05 900 cutting out flames included

Hey all a friend of mine has an 05 rmk that has always ran great with all the general maintenance I have done almost all of it. It has a sno stuff can a fire n ice intake and the radiator removed. Recently the throttle block broke and had to get taped up to finish the day and it started cutting out on him move ahead to today and a new throttle block installed the sled will start and run great until higher rpm then it starts cutting out and popping and shooting blue flames out of the exhaust I'm not really sure what to start looking for here any help? Thanks

I did try that with no luck when it starts cutting out and blowing flames it's at about 6600 rpm