guy at work has a 08 truck with the 4.8 in it. tapping like crazy, heard it across the parking lot at 430am. I walked over to talk to him, he's like it's been like that forever. revs it up and it goes away, idles for a bit and starts tapping again. 200k and he says the truck 4.8 never had the afm. truck didn't even have oil pressure gauge on the dash and he's never looked. just when it gives up its going to the junk yard. not worth fixing.
kinda wild just drive it around tapping. he said it sometimes goes away for months at a time and then comes and goes.