I only paid a tenner for it so nothing lost or gained in my view - it is one of those chambers that pops up all over the net for MZs.
Once I started using it in anger with no mods to the chamber I found that it robbed the bike of what little low down torque it produced and pushed all useable "power" right to the top of the rev range.
So, I consulted http://www.amrca.com/tech/tuners.pdf and then got out the angle grinder and welder.
Long and the short of it is that the chamber as built is way too short for a low reving engine like the MZ - it needs to be a lot longer.
Ended up welding a 10 1/2" long "belly" into the chamber, still not as long as it theroetically should be, but close.
The effect on engine performance is amazing - rides just like the bike with the standard pipe, but feels lot livelier throughout the rev range.
Looks and sounds different (and is a lot lighter than) the standard "drainpipe"
PS If you blow up the image you will see that my welding is not that brilliant - but it does do the job!!