ok so my 97 escort sport has both upstream and downstream o2 sensors, how can i do something the the cat or install headers with out having a ces light come on?

Take out the bulb on the check engine light. Haha

Buy an O2 simulator. It basically plugs into your harness where the downstream O2 sensor would and it simulates an "everything ok" signal. I did this on the Neon a while back. I bought mine at MC Racing.

ya Any ford o2 sim will work, good call guys, and its cheap way to go!

is mc the only place? where can i get a ford o2 sim? whats the best way to hollow the cat any way??

I'm sure you can get the simulator online somewhere. I just happened to be at MC and they had one for my car. This was a few years ago.

Hollow the cat? I remember many many years ago on my truck, the cat was clogged so I took a long breaker bar and put it in one end of the cat and hit it with a hammer to break up the brick and knock it out the other end.

did it on my z, took like an hr and some special tools. def not as easy as it sounds on the ford cat