I have a question for those that have installed custom dual exhaust set-up.... Has your gas mileage increased, decreased or stayed the same. I can't decide whether to get dual or single custom exhaust installed. I would think that a single outlet system would allow for better performance and increased gas mileage do to the lowered back pressure. I also plan on using a Flowmaster 50 SUV muffler no matter which set up I choose. So if anyone out there with a Flowmaster 50 SUV muffler has any info please let me know.