Built one for my own car, thinking about building more to sell. Posting this to guage interest. Proffesionally done, I am a welder with 20 years exp. Mine turned out really nice, comes with 02 sensor bung and flex joint. 4 into 1 equal length, 2.5 inch out. Can't post pics willing to email if you want. I would have to get about $600 to make it worth it.