Drilling holes into a tuned bi turbo would be like
somone buying a K&N cold air intake and then air filter in it.
By drilling holes and releaving the back pressure that the pipe was tuned for would totaly screw the benifits of even having a special exhuast.
If you want a hair more power and it to be louder.. why don't ya just modify the stock exhuast rather then an expensive aftermarket part designed to do the same thing.
Also the bi turbo was engenered to give some of the benifits of.. more exhuast flow.. at the same time as to not mess up anything.. and keep the noise level at an acceptable tone.
If you just want loudness and maybe a small diffrence.. don't
but that just my $0.02
Quack and Zip Around