You call them and they give you an order number or something to that effect. Then you send it to them. I believe mine was a little over $200. They go over the blower very carefully, and if it needs anything, the bill could be higher.
Nitz...It's the GT impeller used on the Cobra for a few more lbs boost. The GT impeller is a little more aggressive design, designed to make it's boost at a lower RPM than a Cobra impeller. Used on a Cobra it's worth 3-4 more lbs boost. This is a better way for a Cobra owner to pick up some extra boost without the extra heat of having to run about 2 sizes smaller pulley, and without the problems of belt slip (on a small pulley). With a power pipe a Cobra can make 12-14 lbs boost with a 3.6" pulley with this upgrade.
I use the up grade with 3.3 pulley and IC.
Like Ralph mentioned you call Vortech and get an RMA # to send the head unit back to them. They go through it and then call you to tell you what's up. My blower was about a year old when I sent it back for the upgrade and everything checked out fine so I only needed to pay for the impeller upgrade ($212.00). They then ship it back to you and you're good to go. Expect about 12+ psi out of the blower now.
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