i have this problem with my 2004 silverado, i replaced my y pipe with a magnaflow high flow unit , replaced all my oxygen sensors, an put on a gibson supertruck cat-back, and my truck will not go threw emissions! i keep on getting a abort! i called the dealership and they told me to put 50 to 100 miles on the truck so the computer will reconize the new parts i put on, and i have put over 500 miles on the truck and the computer is still not reading the new parts! this is gettin realy frustrating. im at my wits end and didnt know if anyone had any advice.