I installed the exhaust in mid aug , so still was running number 2 oil in it…. It is a home job exhaust, but it is pretty much straight back not much for sharps corners on it. I figure it is free flowing because I can hear the turbo whine out the pipe at low idle, and going down the highway. Before the exhaust change you could not hear turbo. There is heaps of power now, but maybe the turbo is running too much. I dunno though.