Test pipe vs gutted cat noise
 

Whew I'm going to get some heat for this question I think! I'm currently running test pipes, headers and a stainless exhaust and man is this car loud! It's not a street car but I feel bad whenever I start it up in my neighborhood, I'd like it a little quiter. With the cats on it's MUCH quieter, I'm thinking of drilling a hole through the catalytic material to free them up but hopefully retain some of the sound deadening. Has anyone ever done this? Is there a noticeable difference in volume? I'm thinking the remaining cat material would act as a glass pack.

I don't see this working out for you.

The secondary cats are made of a metal honeycomb, rather than the more common (at least in my experience) ceramic honeycomb. Point is that you can't drill them out ... and yes, I tried.

http://986forum.com/forums/uploads02...1491322129.jpg

Even so, if you were able somehow or another to drill a hole thru them, you are just going back to, effectively, the straight pipe that you have now. The exhaust gas will seek the path of least resistance, which in this case would be right thru the hole. I don't see any gas willing to work its way into and thru the remaining honeycomb if an easier and less restrictive path exists.

Seems to me that your best bet is to keep your test pipes as they are and just put the stock muffler back on as a trial, if you think that your aftermarket muffler is too loud for your taste.

Good luck - DM