Ok, so I know if you search here you get quite a few results for de-baffling the exhaust. One of which used to have a video that no longer works. I learn by seeing so I though I'd throw up some pictures of what I did so that those of you who may still have questions and want to see it kind of step-by-step can.
This is on an '08 M109R
First off, the tools:
-1-1/4" hole saw with drill bit guide
-1/2" drill bit
Now set up the drill for, well, drilling:
The hole saw goes into the exhaust like so:
This might get a bit tricky just because the hole saw might spin funny due to the set screw in the extension, to get around this I just put a folded up piece of paper between the hole saw bit and the female end of the extension to tighten it up so there was less awkward spinning going on (does that make sense?).
Moving on, once you get the bit in there you'll hit the first wall. You can push hard when drilling if you want but know that when the guide bit goes through the baffle the hole saw might catch and spin the drill so hold on tight.
The first two baffles come out pretty nicely on the hole saw. I found that if you push lightly and let the saw grind through it, the baffle came out with the hole saw. You'll want to keep the drill spinning slowly on the way out, that way its a bit easier to pull out and you don't lose the baffle and/or bit:
Now that the first baffle in both exhaust pipes is out you can do the same for the second. The second baffle is a bit harder to get to but just keep heading back in there and you'll hit 'em. When the drill spins smoothly that means the guide bit is doing its job.
The second set of baffles unfortunately didn't come out as easily as the first. No biggie though, thats where the extendy magnet thing helps:
The first set of baffles are on the right and the second set on the left:
I tried to get a shot inside the pipe of the finished product but it didn't work too well:
Any who, that is what I did. I didn't bother to drill the 1/2" holes around the outer perimeter of the main exhaust hole. I think I'll ride her like this for a bit and see if I want more out of her.
I didn't notice a big change in the idle sound but definitely did in the sound during acceleration. Instead of hissing it gives of a nice rumble now, then when cruising at speed it is a bit mild which I personally enjoy (I can still hear myself think which is always a plus). Well, for this mod. Big fan. Hope this helps people or gives people a bit of reference when trying this stuff out.