O2 sensor questions with tunning

[Burns331]

I have a Grpyhon on my truck that Bill custom wrote me a tune for so that i can run my 5.4l engine on my 4.6l coil pack/ecm setup.


Anyways, i know for a fact that his custom tuning blocks the rear O2 sensors, because when i put my long tubes on and got rid of my cats, i never got a code.


But here in the past year or so my truck has developed a rough hesitation from 1100-1450 rpm. It barley wants to pull through it, but once its to 1500, it runs perfectly. And it runs great everywhere else in the power band.

I also have no relivant codes to this issue.

Does the custom tuning also block codes for the front O2 sensors? Im very close to changeing them out, they do have 225k miles on them.

What kind of symptoms on these ECM's would you get? I know bad o2 sensors can make different symptoms based on how smart the ECM.

Thanks