Engine can't decide where to sit in RPMs when coasting down hill or just coasting
 

I am experiencing that this for the last couple of days. And I have replaced injectors, fuel regulators, all air lines, resealed top and bottom end, replaced O2 sensors and check for exhausts leaks and non. I am literally stuck right now. I even replace the EVAP sensor. I don't know if it would my verbal vavle timing or something super stupid. I've been a performance mechanic for years and right now. I am seriously stumped lol 😆😆😆😭😭😭