Searched a bunch last night and couldnt find a thread similar to my situation and i need help with code 44 (lean exhaust)

I replaced my O2 sensor about a month ago which worked but code 44 is back with a vengance, I have ruled out fuel injectors based on the fact that i rebuilt my TBI and put in new injectors about 3 months ago, cleaned the tank and lines to start fresh with my fuel system along with a walboro fuel pump swap, ALSO Driving around ive been snapping the throttle and pushing it hard with no SES light popping up until i come to a stop and idle the car so fuel doesnt seem to be the problem.

-O2 sensor is new(ish) no wires grounding out on headers

-Missing the donut gaskets on the collector but my o2 sensor is mounted higher up in the collector (edelbrock emissions headers)

- Havent checked for vac leaks yet but im not hearing any and i pick over my motor every time i open the hood

- NO RTV has been used on this thing in over a year so i know its not fouling out my sensor

- Replaced dizzy, wires, plugs and main coil about a month ago, reset base timing with the dizzy swap


My issue here is if something goes wrong i look at the time between the last work performed and the issue, if something is bad or wrong it normally shows up in a few days, ive gone a month or two with zero SES lights or driving issues

I guess im just looking for the causes of code 44, searching thru the threads ive found vac leaks, exhaust leaks, bad o2, grounding wires, things of that nature, and as far as the exhaust gaskets go i havent touched my exhaust in over 6 months and ive been running with no gaskets with no problems, but i think i can try them and hope for the best

any tips?