Ok guys I still have the same problem! I've switched carb out for stock one. Put on original air box. Still sounds like it's spitting back thru carb. I have a stupid question? What is all the sh** inside the spark plug cap? There's a brass screw piece if you remove it a spring & a little aluminum part come out! I took the aluminum part out because it causes resistance in plug wire. Since I took that out could it be causing spark signal to break down & cause loss of spark under load when riding?