I wouldn't buy any cheap and cheerful exhaust parts again.
I bought a Scorpion downpipe not long ago after being offered both a used Japspeed and a used Toyosports one.
I thought that the extra ££ of the Scorpion one would mean it was a bit better but it never lined up at all, I sent it back to them, they stuck it in their jig, said it was fine and sent it back to me. Now I have a second hand decent one and I'm left with a shiny new scrap bit of pipe that I wouldn't try to rip anyone else off with by selling it.
I had to get my car mapped without it for a start as well as I didn't leave enough time

As said buy a real exhaust second hand, most were sold with lifetime guarantees as they were built to last.
J