I recently purchased a 96 with a completely documented top end rebuild for a hell of a deal. During the rebuild, the PO installed a Borla header. Something just doesn't look right. Does aftermarket exhaust normally run this close to the fender well? I have a few O2 related codes,p141, p135, p125 so I decided to investigate further. I have what looks like O2 block off plates and some patch job in front the cat. I see no O2 sensors at all. Not even pigtails. Granted its freezing out so I didn't get deep into the truck yet. What do you experts think of this? I'm tempted to just revert back to all OEM this spring.