You remove the air intake hose off at the filter housing. Slide the turbo into the hose enough to clear the mounting surface when you put the hose back on the housing.
The ones I bought were the correct size with the hose.
The ones I find now are kits. They come with sleeves to fit a few different size hoses within a range, say 3" to 3 1/2".
Chrome JDM Turbo Tornado Supercharge Air Intake Fan Save Gas Saver | eBay