We get many questions about "whats the deal with this billet craze" and its not just that the billet wheel is lighter than the cast wheel, its an entirely new compressor wheel design that is more efficient than the older cast wheel. The old design worked well for many years, but as technology progresses, we get better, more efficient designs. This turbocharger has made 900hp to the wheels in certain applications and comes in a wide range of housing combinations. Most 4cyl applications will use the T3 back housing configuration while most 6 and 8 cyl applications will go with the T4 exhaust housings. If you need any help picking out the correct turbo to fit your goals and budget, please contact one of our experienced sales staff to guide you through the selection process.