What is stage 1 and stage 2?

 

Stage 1 means there are not modifications to your car at all.  A stage 1 tune can still provide more power and better response over the stock tune so it can still be very much worth doing.  On newer Subarus, it will eliminate a dangerous lean condition that exists often when going into boost.

 

Stage 2 means you are adding replacing the factory downpipe with an aftermarket one.  These come in two main varieties, catted and catless.  Catless is more free flowing, catted has a small, high flow catalytic converter.  It can have less raw exahust smell and be a little quieter but can cost more as well.