For the air filter I would wait until you have the pipe. Attach it to the car then take some measurements. Then go to the kandn.com (if you want a k&n filter) and "search for filters by dimensions". Once you figure out what filter you want contact ziggy.

Ziggy also has cheap exhaust systems, https://www.rtmracing.com/xcart/home.php?cat=1554
When I installed the 3" I had to do a few mods, but unless you plan on adding a turbo 2.5" will be fine.

I've got a write up of the mods if you want I can email it to you.