[ByronRACE]

Your engine has not even reached peak torque by that RPM! What is the cam duration on intake and exhaust? If you want to see what this engine is really capable of, you're going to have to spin it at least another 1500 rpm; maybe more. Your peak power will occur somewhere about 1000-1500rpm beyond peak torque. It'll break 450 at the tires...probably 470.

The dip in the 4000rpm range could quite likely be detonation. Why? Your air fuel shows choppy readings, torque drops, then as piston speed increases, it recovers. It may need a little less spark in that range. Read the plugs...see if they are speckled. Listen critically in that rpm range for ping.

Air/Fuel looks quite good. It probably won't get much better with a carb, but if you have some magic way of leaning it out 1/4 to 1/2 a point up high, it'll help your power numbers. If not, we're only talking about 15hp probably.