Engine power cuts out at ~6300 and then drops, revs to 7000+ in neutral

Hey all, I’m running a 14 XP 1000 that I just bought/rebuilt from a rollover. One of the things that was failed when I purchased it was the voltage regulator. Since getting it back together I’ve put about two hours of time on it and it started losing power randomly. Now if I put the pedal down from a stop it will rev up to ~5800 to ~6300 and then slowly leech power till I have to stop again. If I "gently" accelerate and keep it under the ~6000 rpm mark, it seems fine but that doesn’t even get me to 40mph. Tried revving it up in Neutral and had no issues getting it to~7200. No CEL, any ideas?