[universeman]

Thanks all...I went ahead and bought a mechanic's stethoscope (thanks @zelrik911!) and used it to probe the valve covers for loud valves. Cylinder 6 seems to be the loudest and I'm thinking that's where my problem is.

The best place to pinpoint the valve noise I found is actually not on the valve cover itself but on the injector nut for each cylinder...that spot gave a very good indication (without crossover) of how that cylinder's valves sounded compared to the others.

The engine is coming out soon, so there will be a full inspection of head studs/valve springs/guides/adjustments/etc. in the near future. I'm going to continue driving it until then, unless enough of you guys tell me I'm crazy to do that. It seems to run just fine, but a little noisy.