Anyone know if the post cat o2 sensors affect the fuel/ air ratio?

I am wondering because I want to remove all 4 of the cats on my 97 4.2 and put in 2 generic cats. I am worried that I will get a CEL from the post cat o2 sensors or performace/ gas mileage will be reduced.
Any help appreciated. Thx

 

No. The downstream cats only verify catalytic functionality. You may get a code, which might make passing state inspection difficult, but that's it. The engine will perform just fine.

 

I have removed all 4 and put 2 magnaflow hi flows in my 97 4.2. Everything seems fine.
Post cat o2 can control a/f ratio up to 2% or more (so I have read)