Had some Borla header collector mufflers ceramic coated to match the headers and they came back with what looks like a fine sand in the packing of the muffler. I have blown a lot of it out but I can hear more in there when I tilt them up and down. I am worried that if I install them sand will fall back into the engine when it is not running. The guy at Borla thinks it will be OK but I am not so sure. I have the regular slip on collector on it now.