Drilling holes in an exhaust pipe?

i put 2 new thrush turbos on my chevy silverado (4.8L v8) and made it true duels, 2 cats, 2 seperate exits, 2 mufflers. now, i am trying for the loud redneck sound. a bit more detail: i welded all new pipes from the cats back, so there is no leaks. all said and done, it is a bit louder, but not like i wanted. so, in short, i drilled 6 (six) 1/4' holes using a tek screw in each pipe, before the mufflers(so i can run the screws back into it to plug it up if it is too much, or before inspection). i know the dangers of carbon monoxide, all of the holes are pointed down, and i don't sit still in one spot very long anyway. my question is, other than gases, will this hinder my truck in any other way? if so, i will just get the welder out and plug the holes. thanks!