anyone on here have or no anyone with the 3.8 flowmaster cat back american thunder system. just kindve wondering if this is worth the 500?

It's worth it. But you can get it cheaper. 500$ if it's the whole catback, is normal. I'd pay arouind 350-400 for the whole catback. I payed 200$ for dual chamber 40 series flowmaster mufflers and install.