89 Chevy Truck not running right.?

I have a 4x4 with a 350 It does not want to start, once it finally starts it will die if u dont feather the throttle. and motor starts to surge like its gonna die. when u step on the gas it lags and starts to bog down. after runnin it when u pull up to a stop it tries to die. OBDI scan tool says lean exhaust. replaced 02 ECM and checked fuel pressure. also did TBI rebuild and intake manifold gaskets no air leaks. and fuel filter. What else could it be? Thank you