valve chatter 360 magnum

OK, so the noise is at idle, when I throttle it I don't hear it. It's very slight, just noticeable. No, he didn't forget the galley plug or oil would be pouring out of the back, no? Incidentally, my 90 degree oil filter adapter had a leak early on, after a few tuning sessions, and I ended up pulling it off and reinstalling with a different seal; out of curiosity I cut that filter and it was clean as a whistle.

It's a 360 magnum with roller rockers, not sure which cam, but it's new and new lifters. It also has a double roller timing chain.

The oil pressure when I first start it is 60 psi, and it holds while driving for a bit, but after the oil gets hot it drops. At cruise on the highway, it's just under 30 psi, so I was estimating about 10 psi/1000rpm, might be a bit higher but certainly not 15.