my 400 has always hesitated a little when i get on the gas from idle. Not just wot but even 1/2 throtle from idle. I gabe moded my mipe and it got a little worse so i tried changing my main but that didnt help. I asked my mechanic and he said i just need to try dif. mains but that didnt help. I thought it would be the needle but he said that the needle should never need to be changed unless u bore. Is he retarded or is it me but if the prob happens at like 1/4 to 1/2 mostly isnt that the needle.