Toyota Repair: Lexus GX470, better mileage, lexus gx470

Question
I would like to know your thoughts on after market Computer Chips for more HP and better MPG and if they are safe for the engine.I have seen some on EBAY.
Thank You

Answer
I would not recommend this, first of all the term "more horsepower and better mileage" is a myth, you can't have both, more horsepower demands more fuel, better mileage requires less fuel in any given engine, these engines are already designed to provide maximum fuel economy and power, that's my opinion, I wouldn't waste my money on the miniscule gain in either horsepower or fuel mileage that "may" actually take place but the choice is yours if you still want to go ahead with this. I have not heard of any engine damage caused by these chips and I really don't even know if they are EPA approved, ECM modifications must be EPA approved if you reside in the US.