1994 code 44

[drhoward1988]

1994 gmc k3500 CCSS factory 350 5speed.

 

Just installed a set of shorty headers and 3 wire O2 sensor. I was getting code 13 iirc for no 02 as PO removed it. After install I reset the computer (held positive and negative battery cables together). Truck seems to run fun with no miss or rough idle. Also I'm not getting a check engine light. I noticed if I turn it to run the check engine light stays on so I tested and got code 44, which is lean mixture. Here is a list of things I have done previously before I got this issue

 

Headers, 3 wire 02 sensor, plugs, wires, cap, rotor, dizzy, cleaned and rebuilt TBI unit including injectors(ran acetone through them under power). TB spacer, 18lb Pressure regulator spring, new fuel filter, no cats and true duels (PO job), New/upgraded grounds. Converted to traditional 14x3 open air cleaner. I've also already checked timing and it's spot on.

 

I've yet to check fuel pressure since I changed the filter as I was having a problem with it. Since headers and 02 sensor I've put about 100 miles on with about 10 start/ warmup cycles and no engine light while running. Any ideas on what could be causing this issue