if you put a cold air intake in,or a performance chip you will have to have your ecu recalibrate or you will lose hp instead of gain.probably the cheapest way to get more hp would be to have your heads milled,you can get domed pistons,but you have to disasyble the whole engine to get those in. there really is no true cheap way,and in order to get more hp you have to sacrifice gas mileage,The only true way to get more hp is to have higher compression,a longer stroke (for torque) and a cam that has higher lift and longer duration.if you do that you will eat more gas but have more hp and torque.