I have a buddy who owns a 2004 Jeep Liberty. He's looking to increase HP and MPG. I told him the best ways to go that were to reduce weight, get an exhaust, go with synthetic oil and a true cold air intake. Also told him to reduce weight if he can etc.

His question to me was about replacing the coils on the engine to better ones... do they exist, if so where and are they worth it?. and he also wanted to know if it was worth senidng out his injectors to be rebuilt. His truck has 110k on it

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Liberty's have coil packs for each spark plug. From what I know just about everything you do to the engine to increase fuel milage will be compansated for by the computer. Just face it, it's a heavy 4x4 brick and the mileage will always be a little less than desireable. What you have suggested as far as loosing weight is about it. In the stock form, is when the KJ will obtain it's best fuel mileage. These fellows are about your best option --> http://www.bgchrysler.com/