is it true that if you straight pipe rotarys that it can result in boost creep....if so how many cats should you leave in??

 

If you leave the stock intake, you will probably be fine.

But you don't want a straight pipe anyway, because that will be very, very loud. A resonator and a quality muffler go a long way to keep the noise under control. A high flow cat helps quite a bit as well and is a little nicer to the environment.

Oh, and if you are planning on both an intake and exhaust, then you should port the wastegate.