Good news! Pulled the valve cover tonite and it was immediately obvious that #5 intake rocker was loose. Pulled all 12 rockers off. I checked all the cam lobe lifts (Comp 252) and all good. All 12 pushrods are now spinning. Torqued the head bolts to 95 lb-ft, some were at about 85, some didn't move. Then reset all 12 rockers to 1/2 turn preload and cinched the locking setscrews tighter this time. Manifold fasteners all tight. The loose rocker doesn't roll as silky-smooth as the other 11 but I think it's OK.
