i disagree, yea it makes your car sound a little higher pitch, but you can tell the difference over the stock cat. and if you have other mods such as i/h/e and maybe cams, it will be very helpfull. im guessing you got your testpipe from testpipes.com? thats where i did and mine had no place for the sensor either. i had to mark where i wanted it and drilled a hole big enough. then i came to find out that the metal wasnt thick enuff to thread, so i had to find a nut that fit the o2 sensor and cut it to the right curvature to fit on the testpipe, and then weld it on. more work then i thought but you have to have that o2 sensor. hope this helps.