I have a Herst Leistritz muffler - stamped 'made in W. Germany and 03 84 (assume production date?) that came with my car. The exterior is very solid, but when tipped side to side there is slight evidence of small bits of loose particles (rust bits?) inside, but nothing that will shake loose and come out from the tailpipe or inlets. I am inclined to use it when I start the freshly rebuilt engine and then assess it further. Is anyone familiar with this brand of exhaust, i.e. was it a premium, mid-level or low-end replacement unit? Thank you.