My buddy just got a 2010 f150 with the 4.6l triton v8. He wants me to put a muffler on it for him. My question is what size is the exhaust pipe before and after the muffler. We're just gonna cut his factory muffler out and replace it with a performance muffler, so what size i/o does he need?

 

i dont think it really matters after the muffler as long as it is not smaller than org. the pipe before i would keep stock size until more after market mods are done..... like boost

 

from the ones i have seen at work, looks like the standard of 2.5"