345 throttle/choke adjustment??

:banghead3at a loss, adjusted everything, as I run through all the motions with the throttle and choke levers, it appears they work fine, I adjusted the top lever choke that was contacting the throttle, lost the o-ring that goes in the intake stack and tore the front of the tractor apart looking for it with no results, I'm a mess. Runs better as you go down the throttle range, but still cuts out when you get a 1/4-1/3 down, won't hold a low idle and when it gets close, it appears to choke itself. And it won't start back up after it's been running. do I have a carb problem, or am I missing something else??:banghead3

new or newer fuel filter, certainly less than 5 hours

fuel pump is new too, I'll tear into the carb tomorrow and see what's up