So I blew the sled up last year, cylinders were trashed. Pretty sure it was a cold seize. Rebuilt it with all new stuff (cylinders, pistons, etc..) I took it out for a test ride in the field and runs great up until 6400 rpm then it falls on it's face and won't build any power after. So I pulled into shop ckd and reset tps, put another set of plugs and caps on. It has new fuel 91 non ethinol, ckd grounds. It's not throwing any codes. Any help would be appreciated.