My lad uses a DMC Alien.
Great low/mid, with some loss in the high register.
Good value for money.
Very well made, but a little difficult to fit owing to the bolt on exhaust flange.
The flange is like the stock pipe fitting, and has never needed any sealing, or leaked spooge.
IMO it is the best sounding left bend pipe on the market.
The Alien works very well in conjunction with a reed spacer block and a +4 timing mod.