Catless will provide much better electric power gains but unless you might be upgrading your turbos or likely one turbo a significant stream selection will work terrific. We now have an N54 catted vs. significant-stream downpipe manual If you need some more information on power gains amongst The 2. Base https://catless-downpipe53196.hazeronwiki.com/7125845/the_best_side_of_catless_downpipe