Your pump is probably fine and I wouldn't bother to replace it unless you really don't care about the extra expense (labor is far more than the part). That's why I mentioned that the pressure does fall off at high RPM along with boost and didn't necessarily suggest a problem, but if you wanted to be certain you could plot boost vs fuel pressure. I suspect Shad is correct and everything is fine in that area, but the test would put your mind at ease regarding both the pump and regulator. As you mentioned, the AFR is a bit leaner than I've come to expect from the CTSC but they are sometimes a bit rich in the middle then leaner towards the top. If Shad is comfortable with it then I wouldn't be too concerned, assuming that you can trust the wideband in question. Did you monitor it at idle to confirm that it is correct (~14.7) at idle and low loads?
But that still leaves the question of where the power went. Since AFR is reasonable now I guess the ESM isn't freaking out again, but a quick check couldn't hurt. If it is building boost and the AFR is correct the that doesn't leave much. The basics are compression (aided by boost in this case), air & fuel in the correct ratio, spark (no reason to suspect that, but worth thinking about), timing (not generally a problem with the stock ECU), and valves opening and closing.
I wonder if VTEC is engaging? Your power numbers might make sense if you never got off the low RPM lobes. (Edit: on second thought, the power curve would probably be quite different) Or perhaps the VVIS is not opening. The latter can be checked visually and you can even open them manually. Hmmm... the ESM is worth another look. What if it is putting out enough to get out of closed loop, but not enough to trigger VTEC? (unless there is an RPM and throttle level at which it switches regardless of load, I don't really know) I suppose that if it went to open loop maps but stayed on the lower lobes it would probably be rich, so maybe not. But either way, you might want to confirm that both VTEC and VVIS are working. There just aren't that many things that can be wrong.
True story from last week: First time out with my new engine for the 510 it felt a bit rough and not significantly faster than the previous one especially at high RPM, despite a significantly more aggressive build. I did a quick check of timing and a couple plugs but didn't see a problem, so I started to suspect cam timing. But it was late and I was running it in the trailer with minimal light, and suddenly saw a strange flashing blue ring of light. Aha! I pulled #3 spark plug and found that the porcelain was cracked all the way around, right at the base where it goes into main metal portion. The spark was grounding out. It still got enough to run on all four at idle and modest loads, but not at higher ones. I replaced the plug and suddenly had the engine I expected. Funny that it wasn't even rougher, but I guess that cylinder fired sometimes better than others. Now the car can be steered with the throttle at will, which is a blast after doing a spec Miata race where momentum is everything.
Anyway, get your tech and Shad to start at the top of the limited list of possibilities again and knock them off one at a time.