Just had a Flowmaster Non-Delta 40 Series put on my '03 Sport Trac. Decent sound, but not really what I had in mind. What series do you guys recommend for a nice deep grumbling sound? I know I'll never get a V8 sound out of a V6, but I'd like to get close. Any suggestions would be appreciated.

Did they remove the resonater?

As far as I know they took off the stock muffler, replaced it with a single in/dual out and custom pipe to the rear with some stainless tips. It's sounds like a powerfull rice rocket to tell you the truth.