I don't think you'd give up too much flow by popping in a couple of resonators (not sure why/how you'd put them on the y-pipe), they are typically not too restrictive. I gotta think there's a solution downstream of the headers -- zeadlots here in Calgary is running headers on his coupe, though I believe the rest of the system is stock (came that way from the seller IIRC), and his car doesn't sound raspy at all. So it is solvable without the expense of removing the headers. Wish I knew exactly what to tell ya.