I recently had the GT-B wagon re-tuned by Matt for a Phat GT dump pipe.
Apart from the tune, HKS panel filter and DW65c, and zorst, the Lib is stock.
In passing, Matt mentioned it was possible to mod STi/WRX widebody sedan quad mufflers and mid to fit Libs.
Deeper note and slightly better flow to be expected.
I bought a set for $200 and had them modded to fit for $150 at my local exhaust shoppe.
The modding is on the pricey side as tips need extending, flanges need rotating and the hangers need to be relocated.
I'm very happy with the look, and I'll revisit the exhaust shop to see if they can tweak the tips a little for perfect alignment.
The sound is very quiet at idle, boomy at around 1200-1500 rpm (EDIT fixed ) and then has a great raspy sound up the revs...
Off throttle, the popping and coughing is way more noticeable or louder than the stock GT-B muffs.
I recently added an AVO 3" mid to the equation which for me is a perfect combo with the stock muffs - sounds quiet and feels very torquey.
Just this morning I refitted the STi sedan "Mystery Muffs" to the AVO mid, it's still quiet at idle and somewhat louder everywhere else.
The Lib feels a little less torquey with that combo...
I'm wondering if is that something that the ECU will adjust to, or if revising the tune will help with that?
Update:
This mod is being done here with in conjunction with the full WRX STi sedan mid pipe:
viewtopic.php?f=55&t=21958&hilit=+sedan&start=0