I think they are trying to play it safe and keep from people having to build up internals. Keep it small with good boost characteristics will keep the engine somewhat happy. Its pretty simple with the Crs in the Mirage being as high as they are you wont be able to push much boost as it is without popping a HG. Heck mitsu even has small turbos in its mhi arsenal that would be perfect for the little beast. Max out around 8# boost give it a little pep cause lets be honest with as light as it is and the largest rim being able to fit well being 6.5" wide, youll be spinning tires with even that small amount.