Had a GM perfomance (caddy race) lifter on the driver side start tapping at first cold start and then go quiet, only to come back between 2-3k rpm. Only 80 miles on fresh build. Removed them from the driver side, and open them all up and found nothing really, some had what looked like dirty oil trapped under the plunger, but the oil was clean in my engine. Only other thing was some strange machining mark inside the body on the bottom left one , pic attached