yea with my tuner for my mustang i can turn off thing such as the EGR, and the secondary 02s if I ever wanted to run no cats.
I know on my VR wich is obd1 when I deleted the EGR, the carbon cansiter and the rest of that stuff, i simply de pinned pin #10 and it doenst thow codes for that anymore. So i am still able to retain my checkengine light if i have other codes down the road.