X & H pipe vs straight dual exhaust

I had straight duals on my 408. It rapped at low speeds and on decell. I was embarrassed. I went to true rolled 3' out of my TTi's and put in an H pipe. It goes into dual Flowmaster 40's and rolled 3" tailpipes out the rear. It sounds good and I no longer have that stupid rapping problem. My brother always said it sounded like a Chevy before I changed it.