O2 Sensor H-Pipe Question

[bmxelvs]

Ok to make a long story short here it goes... I bought a used 2000 Mustang GT with lots of mods already done, but it wouldnt pass smog so the dealership took it to a muffler shop and had new cats put on. One of the old cats had been gutted or had come apart thus it wouldnt pass. So the muffler shop put on two new ones, only problem they put on the wrong size, and they installed them right where the long tube headers dump into the H-Pipe so the car dropped significant horsepower, didnt want to rev ect... When I jacked the car up the cats were already turning gold (Obviously getting to hot) after only 100 miles, so I took the car to a different muffler shop where I know the guy and paid him cash to cut out the cats and just weld in straight pipe, thus essentially creating an offroad H-Pipe. Now here is my concern after doing this, I have the O2 sensors threaded into the H-Pipe just like they were before only without cats and I am concerned that now the sensors are going to be reading the exhaust as rich and tell the computer to lean out the car. The check engine light has not come on yet like I thought it would. Will this hurt the car? If you go out and by an off road H-Pipe do they have holes to thread in the O2 sensors, or do you just remove them and put bolts in the holes? I have heard something about MIL eliminators, but until I get them can I safely drive the car as it is? Sorry for the long post and thank you all very much for taking the time to read this and thank you for any input.

One last note here is what is on the car: K&N in the fender well intake, Under Drive Pulleys, Pro 5.0 shifter, Ceramic Coated Long Tube Headers 2 1/2" H-Pipe without cats, Raven Mufflers with 3" tips, 4:10 gears with posi-traction.