Bought this muffler and installed it on my 2006 Lexus is350. Seemingly decent quality in terms of external welds, weight and looks until I started the car and drove it about 500 miles. After that, a pretty good thump started to grow. I've tried several times to contact the manufacturer with terrible messages or efforts on their part to fix things. This is EXACTLY not the seller's problem, it's 100% the manufacturer's problem. I'm pretty sure it's a quality issue with internal welds. Will tryโฆ