Hello all. I’m a professional mechanic with access to GM tech line and snap on triton. Just bought this used 2016 Tahoe 5.3 with 141,000 kept getting Flashing cel with a hard shutter. Rpms all over the place and hanging gears when it would shutter. Mostly in lower rpms and medium engine load. Like pulling a hill in too high of a gear. Replaced all plugs with GM and performed BG intake system clean. Still had bad shutter. Had another tech ride with me and confirmed torque converter. R+R torque converter with GM one, new filter and Mobil 1 delvac syn atf. Old converter was replaced 12/21 with CVC converter. Pan had no debris and oil was not burnt. Just typical material stuck to magnet. Still has shutter and flashing cel just not as bad. Cyl 8 misfire. Could bad injectors cause what I’m feeling. Engine runs flawless other wise. I’ve checked st and lt fuel trims and are +/-1. Did not monitor Tcc slip. Am I missing something in the trans or is the engine related. All help is appreciated.