Mishimoto Performance Air-to-Water Intercooler Kit [MMINT-F2D-11K]

This replaces the factory air-to-water intercooler, the heat exchanger that cools the compressed air leaving the turbo before it reaches the engine. Cooler air is denser air, which means the engine makes power more consistently and exhaust gas temperatures stay lower when you are loaded.

why this one — Mishimoto is one of very few brands willing to put a dyno number on a 6.7L intercooler rather than just quoting a flow percentage, claiming +40 lb-ft with nothing else changed, and it is backed by their lifetime warranty. The downside is blunt: at just under $2,000 this is the most expensive part in this category by a wide margin, and the benefit shows up under sustained load like towing or grades, not in around-town driving. If you do not tow, your money goes further elsewhere.