The BSM can is well enuf made, looks good and is relatively light, and what (in Europe) is most important, it is the only aftermarket can certified for the MZ. But it is technically not very good and gives less hp than the stock unit, at least on the Skorpion but I assume on the Baggi, too. Back pressure is always a problem with big singles. You can remove the DB killer if you aren't afraid of the sheriffs or if that is not a problem in your area. That will improve performance a bit. I would leave the original can if you still have it, tho. At my friend EGU's shop
http://www.egu-motoren.de/we had a Baggi from a customer to which that customer had added an aftermarket tuning exhaust system. It was cleanly made and fit well enuf but carried no stamping or label. Subjective impression driving was that the bike was toothless and that was one reason why the customer had brought it in. We put it on the hp brake and - no wonder - only 38hp at the rear wheel. So we put on original system back on and - bingo - the hp went back up to the expected 43hp at the rear wheel. Needless to say, driving impression was much better too. Don't forget that the certified 48hp rating is at the clutch, not the rear wheel.
I had my street Skorpion on the brake at EGU's once, too. Nowhere near stock, so the values as such are not important, but it had at that time 58hp at the rear wheel with a BOS can (illegal and 110DB). With the stock L&W can, it had 57hp. All of one hp difference, but the stock can was legal. There was a big difference in midrange, tho, with the BOS delivering 44hp instead of 39 at 4000rpm. That makes a big difference in street driving and that difference comes from the much higher back pressure of the stock unit. The out of the box new BSM had a full 4hp less top end. And that with measured 106DB!
I personally use a Remus GP can of which I have two, a refraction can with certification stamp and which is really pretty quiet. This one is for vehicle inspection. The backpressure is so high, tho, that it is very difficult to impossible to get the carbs right. Then I have another Remus which has the same number and looks exactly the same but is an absorber, i.e. straight thru with DB killer. THis one is
much louder, but the carbs are easy to adjust. This is the one I actually use, once having gotten the inspection stamp.
In general, it is hard to beat original systems within the confines of legality. This should come ad no wonder since great expense went into their development. They are targeted exactly at the the best possible compromise of performance and immissions at the stipulated RPM for the official vehicle certification. The fact that the L&W system for the Skorpion has only one hp less top end than a completely open racing can shows how much effort went into configuring the can to be quiet at the 4000 RPM where the immissions are measured without killing the top end.
Aftermarket systems are almost always inferior (notable except SR Racing) - or so much louder, that there can be no question of using them on the road. This is not restricted to the XTZ engine at all. It is the case with all brands marketing singles and twins, i.e. engines with big cylinder displacements as opposed to engine displacements. 4-cylinders are so much easier to handle.
All that said, I run a BSM on the competely stock Yamaha SZR, too.
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