Yeah, my experience with flat cam lobes (3 times so far, *SIGH*) has been only about 50 miles or so from "Is that sounding a tiny bit off or not?" to a definate weak cylinder when the throttle is open, and then another 50 miles or so until a persistent miss even at idle.

They can be perplexing at first, because a valve that barely cracks open will still pass enough air to idle well (actually, the increased velocity of the barely opened valve helps it work better than the other valves at low throttle!). So with the hood open, no symptoms, try to drive it and it feels week and rough when you step on the gas. It will still test perfectly on a compression test. And the valve lash might not even be affected - the wear is on the lobe, not on the back side where the lash is adjusted. By the time it misses at idle the valve barely moves at all.
--
I'm JohnMc, and I approved this message.