Glad to read about your turbo mod project. You'll get arguments about whether your turbo needs back pressure or not. The general consensus is that the bigger your exhaust diameter is, the better for your turbo to spool up. No exhaust (muffler) is the best. It's not always true. For your car, I'd go with a 2.5" exhaust. A 2.5" Dynomax turbo muffler should be nice on your car. A lot of guys here have modified their old school scoobies so they should be able to help you out.
I'd be weary of just cranking of the boost. An intercooler is a good idea. I've read that a Saab 900 intercooler should work ok on your car. Also, an air/fuel ratio and an EGT gauge would be a good idea. At least an EGT gauge to look at your exhaust temps.
This is a start. Good luck! I hope to someday own a turbo 1.8ltr engine from one of these guys that is in good condition so I can start modifying it. L8Rs