No u do not need the connecting pipes as Long as u don't mind cutting up your stock exhaust where it meets with your stock muffler.
I have the eisenmann sport on my car without the connecting pipes. Some people have an issue cutting the stock exhaust.
Eisenmann muffler will join to your stock pipes with a sleeve clamp, just be sure to cut at the right place. If u cut too much then u have to get some custom pipe work done at your local exhaust shop. Ie, measure twice, cut once