RXL 650 EFI backfire, won't Rev up

Okay here's the scoop on my RXL, the registration card says it's a 91 but I thought it was more like a 94 due to the body but anyways I can look into that more if it's necessary right now. My brother bought this sled 3 years ago, it would run for about 10 to 15 minutes then it was like you were hitting the killswitch let it cool down for about 5 min and it would fire right back and run great for the same 10-15 min and do the same thing. It was pulling a code for the air temp sensor in the air box so he replaced that new battery new spark plugs new fuel filter the one that is about the size of a car fuel filter. That did not change the way it was running and he got sick of it so there it Sat. I bought the sled from him the next year had to replace the battery again also I replaced the voltage regulator, that didn't fix the problem and I didn't have time to work on it now this year I started digging into this thing.... I could not get the battery to take charge so again I bought another new battery it wanted to start with a little starting fluid but could not get it to run. I was told to check the throttle position sensor so unknowingly I tested it the wrong way I pulled the throttle position sensor out of the sled and was checking it with a voltmeter turning it. Put it back together, found out that the fuel line in the tank was rotted away, so I replaced that and the other inline fuel filter under the air box. Finally it started Idled and ran good for awhile the next morning my dad and I went out to play for a little while and it ran amazing for about 10 minutes then we shut them off geared up and it did not want to start very well but then fired and ran decent for a mile or so, started backfiring on me a little bit the next thing you know it died, it was pulling a code for the crankcase temp sensor, I let it cool down got it fired back up and limped it back to the house but it was like I was hitting a rev limiter... also I forgot to mention that it would idle at about 4 to 4500 rpm and when I was on it pretty good it was running really really high 7 - 8000 if I remember right I didn't know if it was just a gauge goofing up but I could tell from the sound of it she was running high... now I can get it to fire up but running 4 - 800 rpm idle and wanting to die but then idles back up, if I touch the gas it will typically die but playing with the throttle I can get it to rev up but not high enough to engage the track, and it will keep backfiring on me! Sorry for the book here but I'm trying to get all my knowledge of the issues out on the table! I'm thinking throttle position? Anyone ever had this problem!????

RXL 650 EFI backfire, won't Rev up