As an alternative to removing the perforated tubes, Ansa GTS Exhaust chirping can also be eliminated by covering perforated tube holes.
I purchased four 8" sections of "Mild Steel Round Tube 1026 (DOM) 1.500 X 0.065" from Metal Supermarkets (local pickup $35.83 all in), inserted these solid tubes inside the perforated tubes, secured with 1/2" long #8 sheet metal screws and voila - no more chirping.