Why bother. Just take the mufflers off and see what it sounds like. I drove around for 5 months last year with no mufflers.
Then I went catless, it got to loud, I put the stock mufflers back on and left the gaskets out. Car sounds great.
174,000+ miles, 5/20/12 new ej257 short block, 8/20/11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. Also CHECK YOUR OIL, these cars use it.