I don't know about leaking valves on Toyota engines but on LR diesel they just ran rough with no other symptoms.
Hmmm, now you've got me thinking Frank. If that's the case, then it's certainly worth checking. I'll have to have a read in the FSM I think and dust off my feeler gauges, though I do recall a special tool and shims and things so it may not be that simple. With that set up I'm guessing there's no hydraulic tappets.
What you're saying does make perfect sense AND S&S did say injectors or a valve. And I did have more of a sucking sound from one cylinder under compression when I did the BEBs and turned the engine round on the pulley.
Took it for a run last night and the engine seemed a little more responsive, or maybe that was me. However it did seem a tad low on power as it started falling back climbing the hills. Could have been the weather of course.
More head scratching needed and a look at those valves.