Cash that cat in at the metal recyler if it's a stock GM...they're worth good money lol
The cat dosn't interfere with how the turbo works but without it your exhaust will flow better and your turbo spool times will be improved.
With an electronically controlled exhaust cutout(dump) in it's place which as mentioned above is just a Y pipe with a butterfly valve thats controlled from a switch in the car you will have wide open flow from the downpipe and even quicker spool times to help get the most performance out of the turbo setup.
