1999 dodge ram 2500 5.9 360

I removed my cats and started getting a check engine light. I then went to a O2 simulator which runs at a mid setting. My truck is still a fuel hog but i am also running 37'' tires. If i were gonna remove the cats again i would put on high flow cats and new O2. It also may not help that i am running a performance pcm. Good luck.