[Michael C Henry]

I'm at or near 250 ft above sealevel also .The number on the powervalve determines when it is closed .If you mormaly carry 11 inches of vacume a 9.5 will start opening pretty quickly when you step into it.as vacume dropes below 9.5.I'm running 5.5 or 6.5 so I have to step into it a little more before they open ( unless diaphram has been ruptured by a backfire) If diaphram is ruptured it wont close and fuel may leak fuel into the vacume passage for the powervalve.If your just nailing the throttle the 9.5 will start sooner than 6.5 but its just a fraction of a second. The problem is the vacume staying just at or below the set threshold and it drouling fuel in when not needed.
I need to take mine to a dyno tune and see if I'm running rich ,is the spark giving up ,or what I know just enough about carbreuters to be dangerous and I'm the first to say I need help.I'm looking for that zip when I crack the throttle and plugs that will last atleast the summer.I do think less fuel will get me closer to what i want.