ok i am looking into putting in a test pipe...i know this will cause the check engine light to come on and cause a problem with the O2 sensor...does it do anything other than just make the warning light come on?? i have heard that when some cars have engine lights come on that the car is put into a "sleep mode" so it wont perform 100% can anyone help me out with this??? thanks a lot can anyone tell me how to solve the check engine light problem??

There are little "black boxes" you can buy to hook up in place of the downstream O2 sensor that will send back a good signal all the time, so your light won't come on. I know several places sell them, but I don't remember where I saw it last. Maybe try summit.

BTW, I've never heard of anyone complaining of our cars doing this.

There is a simple mod you can do to the O2 sensor. I found it on a Mustang web site. You just need to soder a couple of resistors onto the O2 sensor wires. Let me see if I can find it.

Here is a link to building your own black box. http://www.mkiv.com/techarticles/oxygen_sensor_simulator/

This is what I did. But I made my own. Can't remember how to make them though.
http://www.mileliminators.com/

Found it. Here is how to build your own for very cheap. It works. I am doing it this way. Oh, and it is a zx2 web site.
http://www.zx2racing.com/mods/mods_mil.htm