I have an 08 V6. Just bought two GT take-off mufflers of eBay. I want to have these installed but I don't understand all the options...x-pipe, h-pipe, true duals.....do I need another catalytic converter? I know I could do a search and piece all the answers together. If anyone feels like summarizing the options and specify which option produces the best performance increase.....also the cost of installation of each option...generally speaking. Any advice, any lessons learned from experience...etc....would be appreciated. Thanks