Your Questions - Depends on several things. First I prefer the Dinan exhaust sound. Just a little better flavor to it. The M3 exhaust system comes in two parts. (part 1) Exhaust (muffler) and (part2) the middle flow section with the cats built in. The "M" exhaust by BMW part 1 at $3,500 is full retail. Labor to install about 2hrs. You are paying for the name and the shiny end pieces with "M" on it. They do look nice, but you can get the Dinan with smoke stainless steel ends for $2,199.00 plus ship and install. Please research it. I did, I am very happy with my setup and sound. I also purchased the High Flow Middle Race exhaust and software. Got another 28bhp out of the car. But of course some States have strong emissions and wont allow part 2 exhaust.