03 954 w/ 02 engine otherwise stock

Need Help just had a used engine installed having power loss problems at about 4700-5500 rpm bike acts like its going to die not getting fuel then as I get passed that part power comes back. Then same power loss from 8500-10 grand then power kicks back in. All that is under riding conditions however if you just have it neutral and open wide up it runs like normal. I had the engine put in by a local shop. They used my 03 wiring harness, 03 exhaust (currently getting 02 exhuast) 03 computer; 02 swingarm, 02 radiator. Don't know if any of that makes a different. Dont have the $ to take to Honda dealership so any help would be great

It's gonna be difficult diagnosing it over the net. Sounds like it could be a timing issue so that'd be the first thing I checked. Another thing that can cause this is a throttle positon sensor acting goofy. I just don't know what changes they made from 02-03 that might affect performance.

anything can be helpfull ill check those

see if you can borrow someone's 02 brain.