I have a 91 Mustang Lx 5.0, and I failed emissions. The car has 3.73's, mac equal lengths, and a BBK x pipe. I bought the x pipe from a friend with a mustang, I'm positive his car killed the cats and the o2 sensors. I failed on hyrdocarbons only by 3.59, the composite is .80. If the o2s and the cats are both fried, would this make me fail by that much? What else should I look at, the car runs good, I did a full tune up in march or so. Thanks.