Just replaced O2's and still throwing code!
 

Help!!

My check engine light has been on due to codes P0131 and P0151. I replaced all 4 O2 sensors in my 96 1500 4X4 5.7L and cleared the codes. Went for a test ride and the light came back on with the same codes. What else could be causing these codes? FYI, I am running a hyptertech programmer, FIPK, Gibson headers, and Gibson Cat Back. And the truck has about 97000 miles on it.