What problem is it, exactly, that you are having?
I never could get my stock Bosal replacement exhaust to hang right. And I spent an inordinate amount of money on a BB Triflo exhaust, only to find that the fit was virtually identical. I could have spent a lot of time chasing that down and trying to figure out exactly what the problem was, but instead I spent 5 minutes with a cutoff wheel on my Dremel and made the exhaust opening on the rear valance a little larger.

I suspect it may be that my motor mounts are original and at almost 190k miles, throwing the whole thing out of alignment minutely at the front and thus a fair amount at the rear, but don't know yet, I haven't replced the mounts.