You're not guaranteed to smoke with the removal of the cat and mufflers. It's a pretty good correlation that you might though.
Right now, there are several variations of turbos out there. There are 3 known models (original and 2 revisions), but the details are not clear as to what has been changed with each.
Cobb has been very adament in saying that removing major levels of back pressure (i.e. catless DP) is bad for the turbo and can result in overboosting. I would strongly recommend that you check your turbo model (rev. C is what you want) and keep an eye on your exhaust after a 15-20 min. idle at operating temps. Do this before and after you install an exhaust mod.
The test pipe install did make the car a little more responsive to throttle, and the boost seems to spool up quicker once you get into it. The tone is a little raspier than stock, but nothing obnoxious. Most people won't even notice a difference.