If I put a turbo kit in, can i still keep my cat, or do i need to eliminate it?

Anybody got a kit from Maximum Boost?

If it's your factory exhaust, then you either need a 2.5-3 inch exhaust with a high flow cat, or instead of all of that, you could get an exhaust cut-out. I have a high flow cat, and Magnaflow cat-back, but it's all 2.25 inch so I'm getting a cut-out before I go boost. I have been e-mailing back and forth with Maximumboost asking a lot of questions and I'm happy with their service so far. They've answered all the questions I had pretty quickly. I plan on getting their kit this winter.
Check out the exhaust cut-out here:

http://www.atpturbo.com/root/releases/release091004.htm

Keeping or eliminating the cat depends on your needs and preferences. If you live in an area with e-check or some type of emissions control you should keep one on there. If turboed, you will want to upgrade your exhaust, so a 2.5 cat on a 2.5 downpipe back exhaust will work. I cut and welded my own exhaust and got a Catco converter from Summit Racing for a fairly cheap price.

go with 3 inch piping, that way your turbo would face less backpressure

How much is that turbo?
I wanna get one too, but I'm not sure if I want to build one myself or get one already good-to-go

Yes you can still keep the catalytic converter but the stock unit will be too restrictive in regards to flow. Better to replace it with a high flow unit and make sure you have both pre and post catalyst O2 sensors so you don't trigger any OBD-II error codes.