I also have the 50 Series Delta Flow from Flowmaster - really sounds good to me. Stock pipe is still in place, just had the old stock muffler cut off and welded in the flowmaster. Total cost was about 150 for the muffler and the welding and rehanging. Muffler is noticeable with windows open but not too much with them closed. I like to have the back window down just to hear it.