There are many things you can do to increase the power of your engine. I'll briefly list and explain just a few ways.
1) Decrease air intake temperature
--Decreasing the air intake temp causes more oxygen molecules to fit into your combustion chamber, which then requires more fuel for combustion. This causes the combustion reaction to explode with more pressure, and more power. Hot air intake would not allow as many oxygen molecules to enter combustion, hence making a weaker air/fuel combustion reaction.
2) Increase the intake flow
--It is very important to let the combustion chambers of your cylinders recieve as much air as possible. With a restricted air flow into the cylinders, it creates more resistance when the crank has to...