Help needed with Pipe Exhaust for Z750 L2

I found this interesting.  The L2 uses the same engine and carbs as the E/H models, but makes 3 more HP (in West Germany, anyway.)

Could the exhaust account for this difference?  

  

thanos12 wrote:

I have made the same research. I will wait an owner to post his L2 manual!

So a scan from the parts book, European market, Nov 1981 L1 manual. Hope it helps the general picture.