I have the stock low mounts on my '99 M750. They have been chopped to about 2/3 their original length, but not completely cored. They're not particularly loud... the bike is approx twice as loud and nasty w/ the pipes removed. I'd like to find a happy medium between what I have now and the sound of an open exhaust.

I guess I need to completely gut them out and experiment with packing and a perf pipe, but I can't seem to figure out a way to remove the sleeve w/o cutting off the inlet tube. I glanced over the tutorials and came up empty handed for a complete gutting of the exact pipes that I have. Any suggestions?

One of these in 3/4"-1". Pull off the pipes, then go in from the outlet.

Need more noise? Make more holes.

There are a few ways of doing it but it starts getting surgical after a bit. 

with a gas torch you can cut away the walls and pipes going into the pipe till you hit the front of the pipe.  This way you can stay with the original stuffing.

or you can remove the aluminum sleeve and on the body of the exhaust you will see where the inner walls have been welded to it.  Grind those back and everything inside pulls out (not easy).

If they are like my 03 low mounts coring them isn't really hard, more time consuming than anything. You will have to make some custom plates and have the inner stainless steel tube welded to it. A grinder with a cutting blade will be your bestfriend.

Any luck?

drink lots of beer and plenty of xanax.  I did it once, never again. 

Haven't attempted anything yet. Might be a few weeks before I do anything, been stupid busy at work.

ohh and while your at it hacking away and all shorten the cans to about 3 inches from the hanger.  Makes the bike look super sexy.  

I shortened mine 5" from stock. Its slightly shorter, 1/2" or so, than my tail chop.

 I cut mine down by 50%. Looks great and sounds mean as hell without additional coring.