4.0l Doug thorley headers o2 sensor

I installed the Doug Thorley long tube headers but have yet to put in the URD O2 simulator. Does the o2 simulator have anything to do with how the truck runs or does it just make it so you don't have an engine light on.

 

It just makes it so you don't have a check engine light. It's worth the $150 to not look at the light. Especially if another issue arises which results in a check engine light, but you don't notice it because the light is already on.