probably wouldn't hurt to put a larger main jet in there.there are two bronze nuts on the forward bottom edge of the fuel bowl,the left hand one is the main jet.you'll need a long thin screw driver to get it out.i seem to remember
finding a 96 jet in a sunny a12,but finding a 106 in an a15 carby.if you can find one of these it should help that flat spot,as well as smooth out the idle.you should probably change the secondary jet as well,i can't remember what size they are,but if you can find the a15 carb,grab them both.now,if your carby has the heat shield attached to the manifold,you won't have a hope of getting the jets out while the carby is still on the manifold,the eaiest thing i found to do is take it off & swap jets on a work bench.