If you have two Vtec solenoids your ARE going to be WAY slower. Unless your pushin about 30 psi.

Friend of mine just got rid of his CX with Vtec-E. It was the most gutless car I've ever driven. I have a D15b In my g/f's car to replace the Z6 that broke a rod. I've got the Z6 head on it, and it runs VERY well.

Check your timing. That was a problem we just had with a DA. If you've changed everything else you said you changed, that would be, aside from a leak down, one of the easiest things you could to do try and remedy it.