Buy a bunch of old metal chairs from the church basement and weld them into an exhaust. It already has bends in them so you can just cut where you want to get the right bends. It's going to be loud and you will lose probably 150hp with only a .5" tube.
To be serious though, You have 2 options. 1 is to just remover the stock muffler and get a cheap bent pipe from Autozone that reaches either one of the muffler exits. Pretty much a muffler delete for 20 or 30 bucks. If it's too loud head back to Autozone and find a Vibrant or other straight design muffler. Cut the Autozone pipe to the right length and instal with either welds or clamps(clamps probably to test out first). That is probably the cheapest of all ways.
That will change the sound. Got no clue how good it will sound but that is a chance to take with custom systems. I had a custom 2.5" piping, header, res and Vibrant muffler on my Spec V Sentra and liked the sound. Could sound good on twins, but could sound like crap too.
If it's the boxer rumble you want, then Borla or Rev Works are probably some of the cheaper headers you can get. Just got to be sure they are UEL(Uneven length tubes) to give you that Subaru rumble sound.
Anyways, good luck. Get a sound clip of your choice
