MAC Autosport (Parker) did an awesome job on my husband's custom E36 M3 exhaust. We've had several people from various shops comment on how well it was done. Bonus: you have the car dyno'd while you're there.
Honestly if I was breaking into the motor, I'd send the car out to iND. I've heard nothing but rave reviews from others on this forum.
Just a girl and her 863 ponies...
2013 Santorini M3
2016 328i Alpine White Wagon (Lab hauler)
199x Sapphire M3 (because racecar)