hey everyone. this is my first post on the forum. i signed up awhile ago but i used the site mostly to search topics and get ideas for my own truck. my question is about mufflers. ive searched but maybe i havent seached hard enough but what do most of you have on for SI/DO mufflers? 3" in 2.5" out or 3" in 2.25" out? is there a preference or a difference? i've heard everything from it they sound different to one gives better fuel mileage etc. i have no clue. any opinions are appreciated. oh.. most common length of tip people use? i was thinking 12" length 3.5" outlets.