I still have mine on cause it looks cool, and dont want to go thru the trouble of soldering the manifold closed. The vendor sent me the wrong manifold, and rather than wait an additional week I soldered in my own nipple in using 5/16 copper. Mine is not aluminium it is chromed steel. I silver soldered the nipple using propane making sure it did not protrude into intake airflow. I have gone out riding with the bottle and have pinched it off to try to see any benefit and cannot see any. I have matched my intake and exhaust ports and that made such a differnece I had to move needle to full rich inside carby. Next will be exhaust mod and hopefully thats it.
My 2 cents worth.....