As Alan L, said Dinan is an integrated tune, so in their 2,000+ lines of code, they programmed the water pump to run up to 10% faster to account for the additional heat generated. They also figured out a way to improve the gas mileage despite making more power. That said, the Dinan warranty coverage is still probably a major contributor their tune cost.
Rather than just looking for some additional horsepower, I have sought to improve all aspects my car's performance. Today, I have a car that has been systematically upgraded with Dinan doing the hard work of developing and testing their mods in an integrated manner such that the mods actually work together to improve performance. I have no desire to drive frankencar that works great under certain conditions and maybe not so well under other conditions. Today, I'm just patiently waiting to see what Stage 4 will bring.
