1.You'll probably have to find out if some of your valves are sticking!!!

2. Make sure oil pressure is at specs and oil level is good ( VTEC wont work if its not)

3. Do a compression and leak down test

4. take your spark plugs out and see if your piston is wet. ( it may be number one if so)

I kno some of this cuz it happened to my cousins car. After 5500 rpm the car failed to make power. On the dyno the power curve kept increasing until 5500rpm then it fell off. Im not a shop or anything just a few suggestions.

Hope this helps