valvetrain noise 5.9 magnum

Today I noticed some noise coming from my engine while it was at an idle and it really seemed to be coming from under the the passenger side valve cover right at front, ether that or it is coming from under the intake manifold, right under the carburetor. I did a compression test on the engine and every cylinder is at 150 psi engine fully warmed up and carburetor wide open while cranking. And I am 4000 feet above sea level.
I have not over reved the engine ever since I got it and I have a rev limiter set to 6500 rpm.
What are some possibilitys here? Rockers? Valves? This engine was bought brand new in 2002 it's a 300hp crate 360 magnum and its got about 20 to 25 thousand miles on it.