I was looking at getting a cobb downpipe for my stock exhaust but will it be more beneficial if I got with a different company and buy DP/full exhaust combo? When I say beneficial I mean in terms of hp gains. Also if I was going to do just the DP which one should I go with? I'm planning on installing it and then going to P&L to get it tuned. Sorry if I'm beating a dead horse here but I couldn't get exactly what I needed from searches.