The electric fans (if they pull as much air so you dont over heat ) will give you more hp ,but 18 rwhp is not going to happen ,you will be lucky to get 2 or 3 hp . as far as a tune ,that will be a problem in the heat of summer in hot climets. if your looking for fuel milage a 160 therostat is NOT the way to go . the tune is nice and good for a very modest bump in hp in the winter ,but once the outside temp reaches 95 or more you will need octane booster or you will get detonation and the computer will retard the timeing and your power and milage is going down not up . now if you live where it is cold year round the tune will work .
at 6500 lbs a shape like a brick and all wheel drive the H2 is never going to be a fuel thrifty vehicle .enjoy it for what it is ,a great truck for on and off road that can transport 4 or 5 people in comfort on most any surface .
all these mods cost money and are a source of revenue for the company's that make and sell them ,so when you hear all these claims of big HP and fuel mileage bear that in mind B4 parting with your money . remember a salesmans promise is like a prostituts kiss .