Exhaust Cut-Out/Diverter Question

I just got my exhaust cut-out/ Diverter from Street Pro and am really looking foreward to putting it in this weekend. The only problem is that I have one diverter, but two pipes running into the muffler. Would it be harmful to install it on one of the pipes and have the other still running into the muffler? Would it still sound good? What should I do?

Thanks!

Went ahead and took it to the exhaust shop on saturday...We got it up on the lift and discovered that there wasn't really any place it would fit. We decided to take out the exsisting 70 series muffler, replace it with the smaller 40 series to make room for the cut out. The guy welded a Y pipe on first to make the duel inlets down to a single 3" in. Then came the cut out followed by the muffler. I had him weld a bypass pipe from the cut-out back into the exhaust pipe after the muffler so everything would exit the same place, open or closed. The end result is very beautiful....and LOUD.