I watched the install video provided by BC and it says to, "carefully remove the pipes from the CAT as the gaskets will be re-used". That tells me no gaskets are provided with the hogslayers and they expect you to be able to use what's there.
Perhaps your pipes didn't come off as cleanly as they're supposed to.
I'm thinking of getting the hogslayers myself and will look forward to hearing how this works out and how long the delay will be. I guess one solution is to order gaskets up front so they're on hand when you install.