Just got my muffler installed here:
Kartek
11480 Gateway Blvd
Los Angeles, CA 90064
Neighborhood: West Los Angeles
(310) 477-7475
Home Page
Kinda random location but the guy who worked on my car did an amazing job. I brought my own muffler and it was $100. Custom stainless steel brackets, amazing welds, and just the angle you want. I'll take some pics if anyone wants.
+1 for these guys if you are near the West La area. If not, it is worth the drive.