EDIT:I posted late

Do what andrew did. Get a stock muffler. Stick it in. Then instead of attaching your DP and midpipe to the stuck muffler, just have your mid pipe dump the exhaust right before your muffler.

Basically you're using the stock muffler as a decoy.

Or you could get a more quiet/restrictive system, and have an electric cutout installed at the bottom of the downpipe.