I have a serious headache, I installed a FCR carb kit and now my idle is all messed up. I thought maybe I missed something, so I went back through it. I took it apart a few times and found nothing, I switched between 155 and 160 jet and it made no difference, I left it on the 3rd clip. I have a FMF pipe and 3x3 done, no other major mods, and I'm at  2,500 feet. I removed the slow air 100 pilot jet and set the fuel screw 2 turns out. It runs good, but idles high after coming off full throttle thens slowly comes done till it back fires and dies. Any ideas? I played with the throttle cables to ensure they were not sticking.

What is the source of the carb kit? New carb? 39mm FCR mx?

Sounds lean. Put the air jet back in.  Air leak?  What pilot jet?  What needle code?.  The main jet will have no affect on your idle issue.

It's the thumper kit, did everything per the instructions.

You need to fine adjust the fuel screw. Ensure the throttle cables have a little bit of play.

You are going to have to help out a little more than that.  Thumper kit from Thumper Racing? or Thumper Talk? or???

Presuming it's the 39Fcrmx conversion kit....Did you follow this guide?

http://www.thumperta...ing-the-tt-kit/