Sorry if its been gone over before but i dont have time to search for the answer.. Im installing a Downpipe to the stock catback i noticed they use an exaust donut gasket on the stocker . I also noticed that my downpipe came with a regular exhaust gasket so should i re use the donut gasket? Or use the gasket they sent? i dont want to have a problem with leaks.. also do most people use the stock heatshield im pretty sure its not gonna fit should i just hack it off till it fits? help would be appreciated thanks..