I have the same set-up. The gasket is a really hard metal with a thin strip of soft cotton like material on the outside. Honestly, I was excited when I bought the cans and couldnt wait to try it out. So I used the same gasket and dont seem to have a leak. Since the cans are so easy to install, I did go to the dealer and bought new gaskets afterward. Now the question is, when am I going to put them on? Another alternative, use the old gaskets and put some of that blue silicone type of gasket sealer/maker. It has a name, I just cant remember it. If I were U, just buy the gaskets. They're cheap, about $5 a pair. Do it once and do it right.
PS: U will love how they sound. People told me they will sound just a little louder. WRONG!