[HummerJim]

I agree that those chips are just a rip off. To make more horsepower "RELAIABLY" you need more cubic inches. The Lycoming 0-540 (that's 540 cubic inches and a 6 cylinder) produces 260 horsepower in a Piper Comanche at 2500 rpm and some have gone 2000 hours over their recommended TBO, that's the equivalent of 250,000 miles in a vehicle if you consider the fact they are always under load, just like a boat engine, very little unloaded time.
Cubic inches make horsepower and the weight and aerodynamics of what you're moving determine mpg or gallons per hour PERIOD. If you limit the cubic inches then you have to go with the heads, the compression ratio, the cam, the valves, the chip, the induction system and you seriously affect durability. I know you probably know all this, but take it from an old fart who used to race sprint cars, when you soup them up, they like to come apart. I had a chip in a Corvette and it did very little for it except make it hard to start in the winter and when it was hot.