I need HELP......
What is SI, DO, SIDO, DODO, what is true Dual Exhaust and what are the differencesbetween manufactures, what are blast packs?
Oh yea, does the gas milage really go up or down??? I was told your car can breath better and gas mi would be better......

 

SI=single in, DO=dual out, so SIDO has one pipe coming from the catalytic converter to the muffler and two coming from the muffler back to the tips. true duals are seperate pipes from each header back to the tips. never heard of blast packs but glass packs are a muffler that has a fiber glass material in it that improves the sound especially over time to put it simply. picking a manufacturer is all personal preference when you go with any of the big names such as borla, magnaflow, gibson, flow master, bassanni. mpg may increase slightly 1-2 mpg depending on your application and how you drive, the size of the pipes ,etc. hope this helped. check some of the old posts for better answers these guys no alot.