wasp .28 breakin and tuning

[squeeforever]

i have a wasp .28 i have installed in my jt racing t-maxx and went to break it in a little while ago and its acting kind of funny. first off, it is running about 230 on average but i got one reading of 300 for some reason. another thing is the carb was set at 3 1/2 out on the high speed from the factory. its now at about 5 1/2 and still running 220. also, there is this little screw im not sure what it is. it is on the oposite side as the low speed and is not a needle screw. what is it? how far out should it be and should it be adjusted? any help would be appriciated.

EDIT: it is also sounding kind of funny. it is almost like it is studdering. like na na na na na na na na na (if that helps) instead of like my revo that sounds like naaaaaaaaaaaaaaaaa...