08 Jeep Commander 4.7 knock

I have an 08 Jeep Commander that has a knock. I
pulled the valve cover off and checked all the
rocker arms and lifters they seem to be fine. Check
the flywheel for cracks replaced it no problems
there. To me the noise seems loudest coming from
the exhaust right before the catalytic converter. I
check the volts both pre and post on the oxygen
sensors front oxygen sensor is rapidly cycling rear
oxygen sensor is stable at .7. the problem started
after I shared water pump and lost a fan belt
replace the water pump and that's when the knock
developed. I hear the knock at idle and when under
load but when decelerating seems to go away. I
have no codes coming up. Oils been changed.
Added oil stabilizer. Just ran seafoam through no
change.