I was getting a check engine code for 21 (main o2 sensors) so i pulled them and cleaned them.
I reset the ecu and drove it for a week, now im getting code 25 for lean a/f mixture.

I read some where that an exhaust leak could cause this. I deleted my egr system a while back, but couldn't get to the exhaust tube bolt on the back of the engine so i just cut it short so it doesn't stick out and left it open, could this be the culprit?

 

If the issue wasn't happening right after you deleted the EGR system, than it might not be the issue, though it might cause an exhaust leak... And I would recommend just replacing the o2 sensors. The main bank 1 sensors are around 90 bucks a piece.

 

Well it is leaking exhaust for sure. The egr tube is dumping it in the engine bay. And I cleaned the o2 sensors and the code for them went a way.

 

Glad you got it figured out....

 

Oh, I see...never though o2 sensors were reusable...
Good to hear

 

Well it's not completely solved. I still have a code for a lean afr. I'll just try and get my car on a rack and plug the egr tube flange on the header, hopefully that fixes it.