Ok, replaced both O2 sensors (they were really old anyways) and it seems to have more power -- however, I am still getting some knock at times, it's very unpredictable though,, I can hear a faint "rattle" in OD at low rpms. I also have some lifter noise upon cold startup which may be related?
Which direction should I pursue now?
Ps , engine has only 109K on it so it's not exactly high miles.