personally go i would go with the muffler. till the tranny goes and 5 or mt is installed (if thats your plan). i redid my whole set up dual no cats not thinking of that. once my tranny goes im redoing mine simalar fixing minor defects (placement and products used). i will have to disconnect all pipes during the tranny swap and renstall or just redo the exhuast. i have awhile before my tranny bites it. so i figure it was a good thing i replaced to run on for at least 2 or more years.