jetting???

[Adam 250sx]

i have an 85 250sx with a cobra pipe and uni filter. it bogs out when i crack the throttle and seems to run better when the choke is on a bit. i have tried changing the needle positon and other carb settings but nothing seems to work. what size jet should i try.as far as i know the stock jet is in it now. any help appreciated thanks :?

[Dirtcrasher]

Did the problem start as soon as the pipe and af were installed?? Off idle is the air screw under the carb, it has recently became something I hate. If I mess with that screw I get good throttle response but it won't start in the cold - POS. If you haven't already tried turning that screw give it a shot - only mine is an evil satanic worshipping air screw.