Go 2 1/2" on the exhaust, some may say 3" it all depends on your goals. I'm going with 2 1/2". As far as intake goes, there's not a vast amount of options. If your still going to be running the 1g MAS then your can upgrade the rubber intake pipe to a aftermarket one, if you decide you want to do the 2g MAS conversion same goes with that one. If you want to run a GM MAF then you can eliminate the 1g MAS, vent your BOV depending on where you install the GM MAF, and just run some regular intake pipe with a intake filter on the end. There's a few options as far as intake.

So far it seems your off to a good start. Maintenance is the key to these cars.