I was expecting the mixture settings to need to be made richer so I did a bit of experimenting with the needle and slow running settings.
In a nutshell it runs best with the same settings as it did with the standard silencer, make it richer and it just looses performance, particularly at the top end of the rev range, in fact too rich and it will not rev out.
I have been riding it just as hard with the chamber fitted as I did with the standard pipe fitted, and if I take the plug out it looks a good colour so now worries that it is going to seize ir hole a piston.
I can live with the change in "power" characteristics.
Hoping to have a set of spannies arrive for the H2 shortly courtesy of Jim Lomas as I did not want to go through the Higgspeed experience again.