Gee Brent, with all the replies to your problem, you may not get a chance to try everything.
Since the valve train has been adjusted multiple times, I do not think the cam bearings are going bad.
You may want to pull the lifters and put a set of presoaked, pretested, out-of-a-test-engine, regular lifters and adjust down to stock settings to get the engine running and without events.
After it has been running, try adding a lifter. See if it, by itself works in your setup.
With all these variables, it is going to be very hard to pinpoint a problem.
Get to a working base and work with one variable at a time. It may take a while, but you should be able to isolate the overall problem.
I hope this helps.
Trularin
