This is really not the kind of engine anyone should be taking to 12,000 rpm.... or even 9,000 for that matter. Testing how an engine performs in neutral really won't tell you much about how it will go down the road. An engine working under load usually behaves quite differently.

Does it have problems when it's on the street and not at 9k rpm? Also, it sounds like you may have a valve or engine noise.

CC