Riding mower engine only runs on full throttle with choke closed why?

This is an older 2 cyl briggs and stratton engine. Rebuilt carb and installed all new gaskets on intake system. Cleaned all carb pages with carb cleaner and high pressure air but when i start engine with choke open runs fine but as I give it more gas the more the choke needs to be closed. At full speed the choke is pretty much closed. I cant find any air leaks and i think its getting enough gas but just not shure. Engine hasn't ran for 1 yr bringing it back to life but i know it worked fine before that. Rebuilt fuel pump as well and tested fuel solenoid for proper operation. Only thing there is a little blow by coming out of one cylinder more than the other but i don't think that's the cause.Can i get a few pointers on something im missing.