Any explanation why this does this after exhaust and PCV mods?
Sounds like a tuning issue more than an exhaust issue. I have a full Muzzy's (for a ZX-14) and I didn't notice any loss of power anywhere in the powerband. On the contrary I felt a little more pull through the whole rev range. What tune are you running? If a new tune doesn't fix it you could think about an auto-tune or an actual trip to a dyno. I have several good tunes that I have used. My current tune (I would be happy to email it to you) is one that Wanderlust sent me that he uses in his PCV. It was made for Muzzy duals, flies out, and K&N IIRC. My bike runs like a raped ape.