Im looking to cut the cats and res out and it appears that diameter of the pip is slightly smaller at the cats. im guess 2.75" then enlarges to 3" for the res. Am I correct or should I just use 3" for the whole thing?

This is how mine went

i used a 3' for the resonator. i didnt delete my secondaries

is your exhaust loud at regular highway speed ? I mean i want to have custom quad exhaust but i just dont want to turn into a loud honda if im only doing 3k RPM on the freeway.

no. once going a steady speed, it isnt bad. i also drive with music and/or windows down.

but when windows are closed and music is off, there is an ever so quiet/slight drone; barely noticeable. i wouldnt say it is loud unless i gun on it on the highway. 3K rpm will not be a problem at all.

oh...and i also have headers

thanks man im definetly going to get one now i have the difuser i just dont want to put it on without the exaust to match that just looks too ricer for me lol. about how much do you think independent shops would charge for custom quads ?

not sure.
check out this recent thread for info about it. the USEFUL stuff should start around post #5

https://mbworld.org/forums/c-class-w...uys-think.html

hope it helps. and it will certainly sound AND look good. what kind of muffler(s) are you looking to use? C55?

did you get a C55 spare wheel tub? Do you have muffler on each side?

i dnt think he has duals, the two pipes connecting is where the pipes after the headers meet and become one..