Rocker noise

[PRL]

I've done some research on line, and cannot find what this problem is. When I drive on the highway at 100 km/h for 30 minutes I start to hear my rockers clatter. At first my oil pressure would drop at the same time, but since doing an engine flush with sea foam and changing the oil and the pcv the oil pressure now doesnot fall as noticeably. I'm wondering where the preblem would be? My suspicions are the oil pump or the lifters, but I'm not very good at trouble shooting. Thanks in advance for any help I receive.

[Conanski]

You may have knocked some hardened gunk loose which is now partially blocking the oil pickup, time to drop the pan before the whole motor lets go.