I have a1996 indy 500 that does not have the original carbs. All of the jetting is correct for that year specs except for the needle jet. The needle itself is the right one. The problem I am having is that is loading up all the way to half throttle and then it clears up and really rips. It loads right back up again when below half throttle. Yes, the air jets are clean and unobstructed. I am familiar with the stages at which the carb regulates fuel throughout the throttle points but am curious as to whether the wrong needle jet would cause this issue. Everything else has been checked and rechecked numerous times and same issue. Chokes are set correctly with new plungers, no airleaks ,and fuel pump diaphram is good. It idles fine but rich. I think that the taper on the needle with the wrong jet would allow to much fuel by until the needle is withdrawn to the 3/4 to full throttle position. A local snowmobile mechanic says that would not affect it like that. Does anybody have an opinion on this? oh yeah,to get the thing at the correct idle speed, I have the idle screws bottomed out and they are the required 2.5 cutaway slides.