owner certified applies to any mod under 15% capacity, and not rquiring any structural modifications (ie custom mounts etc). the engine must also be "as the factory intended" with all emissions gear etc connected. NO modifications allowed whatsoever.
for forced induction you need to multiply the cc'd capacity, and this will usually push you over the 15% capacity ruling.
power output increase is at the descetion of the inspector whom you try to pass the engine through for a brown slip.