I would have updated my old thread but it's buried now. I've been tuning a 1996 Summit 670 that has twin pipes, no HAC, and some other upgrades. Back in December I went through the rotary valve gear so the engine is fresh. It's been fun getting the jetting right so today I added Powerjets. The install went smooth, drill two holes per carb and tap them for the powerjet and feed. It took just over an hour to set up both carbs. The result? All I can say is "WOW"! Throttle response is crazy, it now wants to pull my arms off while it pulls the ski's up. With the twist of the knob I can go leaner or richer, depending on what the egt is showing. Thanks Modman for the recommendation and the pdf, the install went smooth. I can't wait to get this thing out in the hills to really try it out.