Congrats on the 993, and welcome. I had my suspension replaced by RAC, formerly Ruf, with parts (RoW M030 springs and sway bars and Bilstein HDs) purchased from Vertex(?) in Florida. Since RAC broke ties with Ruf, I've heard they are not as willing to install customer supplied parts since they now sell them, too. I have also had standard maintenance performed at Boardwalk Porsche. They have a pretty good air-cooled staff, but they charge dealer prices and aren't good at performing non-standard Porsche mods.
I have mixed feelings about my Fister IIIs. Most of the time, I love them, but occasionally I think they are little too loud. The disclaimer is that I am not a fan of really loud exhausts. Also, I may be the only one who thinks they drone (around 2800-2900 rpm). My son says it's not droning, just the rumble of the exhaust.
Dan