I doubt fuel pressure issues; acceleration is superb, smooth and responsive. Would there be other symptoms? The plugs were not fouled at all so I doubt the cat is bad (fingers crossed on that one!). I've read a lot about valve issues with these engines, but that diagnosis is beyond my abilities/toolbox. I'll have to take it to the shop I guess, as I feared. I'll pass along your suspicions to my mechanic as a starting point. Thanks for your time.