I went with the MF 11229. 3" in and out as the flapper valve drops down to near 3" into and out the stock muffler and had removed the rear flapper. Wow start up, idle and throttle sound great. Cruising not so much, you can hear the DFM, and it sounds busy switching all the time, and there is drone in DFM mode while under load till more cylinders activate. Ill be getting the rear flapper put back in, I am sure it'll kill the startup rumble but the on throttle sound will be great and the dfm chop and drone should be gone.