My neighbors high miliage 5.3 was doing the same exact thing. Believe it or not after asking around and being told that there were some bad oil filters going around. He tried this first and it fixed the problem. good luck buddy.

 

Well, I have tried the different filter thing and when my pan was dropped, it was clean. I wish that was the problem. If it was this lifter problem, wouldn't it fail and then have a consistent, noticeable effect on the oil pressure? What I mean is, my problem is consistently getting worse(harder and harder to build pressure). Does that mean I have another one fixin to fail or is one bad one enough to make it where it won't build any pressure. I am afraid that before long, it may not build any pressure at all. And if it were yours doing this, what kinda cam and lifters should I get for a moderate performance increase?

 

Well, after a new oil pump, sensor, filter and a lifter swap, the enemy finally showed itself. It was the seal at the camshaft retainer. Holy crap that was a lot of time wasted and money spent trying to figure this one out. Hope this may help someone. Good luck