I know exactly what you mean "hits a wall". Mine bucked. Unfortunately I am no help, because I never really dissected why my y5 did that EXACT same thing with the crower regrind. I'm just here to tell you there's someone who feels your pain.
I had a sneaky suspicion, though. With my cam, I told them to regrind the large intake lobes only, and leave the smaller intake lobe(if you can call it that) alone. I *think* that with the difference in base circle diameters, the cam could not line up the vtec dowell. I had a feeling that this was part of the problem.
Crower never did one of the y5's before either... I tried to relay all the necessary info to them regarding anatomy of the rockers and such, but they ignored me. I also take some blame, as I requested that they leave the base circle on the smaller intake lobe alone.
Crower thought the intake lobes were the exhaust lobes, and vice-versa...