I’m a Detroit mechanic but sometimes we get cats in the shop. I’m not to up to par with cats. We got a c15 acert with low power. I’ve test driven it twice. All sensors on cat et appear to be working, it has good boost. 46 psi going up a hill. Injectors appear to be working when doing injector cut off test. Fuel pressure is like 85psi at idle at the secondary fuel filter housing. Any ideas anyone?

edit: forgot to add. This truck was smoking some , another mechanic at the shop replaced and Iva, and that helped. The customer says it still smokes some but since test driving it twice I haven’t noticed smoke. the power just feels weak Even tho boost is good. And yes the accelerator pedal reads accurately Up to 100%.