Your 1989 chev truck shows a code 44 but the exhaust is rich under loads you have changed o2 sensor you think map sensor please help?

code 44 -02 sensor indicates a lean problem,code 45 is a rich problem,check the ecm wiring connections,#15 and#8 check also for a vaccum leak at the tbi base gasket.a code 33 or 34 indacates a faulty map sensor,my 89 Chevy 4x4 read code 44 followed by code 34 which turned out to be my vaccum line to my map sensor was off.