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Ed,

Your hot idle problems may be due to air in the fuel.  I had very similar
symptoms of good idle after start and taxi to the runway.  After the flight
the taxi back always included turning on the boost pump to keep the engine
going.  I always attributed this to vaporization.  It turns out that the
culprit injecting air was the Dukes boost pump!!  When the boost pump was
off it sucked a little air into the fuel and when turned on it stopped
producing air.

This took a long time and effort to find. The effort included cleaning and
checking the injectors, flow checking the servo, replacing the mech. fuel
pump, putting an air cooling shroud around the fuel pump, and making sure
that all lines were well insulated.

Don Rivera of AirFlow Performance suggested putting a clear plastic tube
temporarily from the fuel servo to the flow divider, start the engine, and
look for bubbles of air passing through.  There should be none.

I found bubbles. Next I connected a fuel line from a gas can to the mech.
fuel pump and the problem went away.  Next I by passed the boost pump and
the problem was still gone.  Hence, the culprit was the boost pump.  A new
boost pump solved the problem.

Hope that this helps.

Hal

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