I have run three different mid pipes on my cobra.
BBK O/R X-pipe, sounded like complete crap with my flowmasters dumped, went with the flowmaster american thunder cat back and it still resonated like crazy. I then went with a BBK O/R H-pipe, it had a great sound with my flowmaster cat back. I then switched to a 99 cobra motor, exhaust manifolds were different so my 96-98 pipe would not work. Thats when I bought my VRS O/R X-pipe, by far my favorite, a little raspy with the flows, it is louder than my old H-pipe, but the thing sounds just sick under WOT.