Just lightened my muffler with this DIY mod. Took me long enough to get around to it, saw the thread when it first came out.
Drilled ¾" holes in my fixed tip 2000S using a stepped drill bit I got at Harbor Freight. I've seen these bits at Home Depot also, I think they were Dewalt brand. The small tip of the step drill doesn't have the tendancy to wander around as much as a full size bit and I didn't have a lot of trouble getting it to start drilling at the bend in the pipe. I mounted the bit in an Irwin 12" drill bit extension and angled the bit into the pipe, letting the extension ride on the inner edge of the exhaust tip to brace it. The smooth shank of the extension didn't even leave any discernably marks on the edge of the tip. The only hassle was I had to grind the shank of the bit round to fit into the extension, since it came as a hex shape. The only mistake I made was to angle the bit upwards when I was drilling. The bit ran into the pipe that connects the center chamber to the end chamber after I broke through the first pipe. Luckily, the bit is short enough that was still able to finish drilling without drilling into the other pipe behind it. I put some scratches on the inner pipe, but unless you get down on the ground with a flashlight, look into the exhaust tips and through the first holes, you'll never see them. So in hindsight, keep the drill bit level. Oh, it was fun sweeping all the stainless steel chips from the driveway the first time I started it up after the drilling. They come spraying out and make a weird noise as they come out the tail pipe. At first I thought I had done something wrong because the sound was so strange. The metal chips must make a swirling/rattling noise until they get blown out. A good reason to take the car out to blow out the muffler with some high RPM's.
Just like the previous posts, the sound is throatier and a little more burblier (sp?) at lower RPMS and I notice it some when accelerating and deaccelerating more than before. Other than that, the perma-grin gets even bigger. Sound more like a sports car now.