Hey Scottmech, I was hoping you could help me out with a few questions. I am looking at getting your downpipe w/ cat or possibly the interchangable downpipe. I go to the track frequently and I was wondering if getting the highflow cat would be sufficient or if I should opt for the available interchangable dp? I have to have a cat since I live in california so a straight race pipe will not work for me. I like the idea of changing between the two options but is the power significant enough to worry about it? Can I do this at the track with a jack, and how much of a pain is it to change out? Will it have a tendency to be more prone to leaks than getting the system w/ the highflow cat welded in? I hope you can answer these questions for me as it would be most appreciated. Thanks in advance and I look forward to a response. Anyone else on the forums viewing this feel free to chime in as well with your thoughts.