dudes i have a custom made cat back exhaust the piping is 2 and 1/4 inch diameter (stock is 2 inch diameter) stainless steel and i removed the 2nd cat and the muffler is 4 inch titanium (stock is 2 inch muffler) and it only cost me $134 ($54 fot the titanium muff got it off of ebay, and $80 for...