AFM Oil Filter

That's right, I have discovered there is an oil filter for the lifter oil flow.

This filter is mounted behind the oil pressure sending unit. The sending unit must be removed to change the filter.

GM suggests removing the intake to access it; but a number of Youtube vids suggest the filter can be changed by removing the pressure sending unit and "feeling" it out.

Roaming around on the web, suggestions are to change this filter about every 50,000 miles.

As well as limiting oil flow to the lifters, apparently a clogged filter will also create the low oil pressure warning that some members have reported. And this is easily seen, as the oil must get through this filter to pressurize the sending unit.