KDX 200 starving?

i've only had my 87 kdx for a few weeks, but when i go out riding, it just seems to be lacking something: example, when i first crank it over it acts like it's being choked out, then it warms up and runs good ( for about 20min), then if i get anywhere above 2nd gear and try to actually get on it, it acts like it is starving for fuel. I have done the following: clean KIPS, cleaned carb., including needle valve, checked condition of fuel petcock(not very good), ordered new carb manifold (should be in today, old one in terrible shape).......any ideas or recommendations?

the petcock really needs replaced, but i've been trying to budget my spending at the damn dealer!!!....reeds look good to me, they were in gap spec (unskilled in the reed department though), have clean all jets, new air filter w/ oil.

honestly it's sad to say i'm not sure of the jet size, i believe it to be stock, but wouldn't bet on it....current carb boot is in terrible condition, thus this has been what i'm hoping my new carb boot will solve?!!!