I have an ongoing situation with my PA .65 RE  I realease it & the thing takes maybe 3 laps & it has increased engine speed a lot    I have a .192 venturi in it the head is pinched down a bit , the pipe is a Randy pipe .65 Ultra Torqure from 2000   13-4.25 Eather Wide blade  .Any ideas how much pulling the pipe out will make or not? The pipe is  set a 17.6".
  John

hi Randy,
  I normally set it for a ground release in the lower to mid 9s  9200 to 9700     ground release   it does it with the thinner props at a higher rpm also   say 10,100  the fuels are Sig Champion fuel 10%      , GMA 10/22 , ROjett  10% all synthetic,  Byrons 10% all synthetic   I add Areo 1 & 2 ounces of castor in the all syn fuels.  I thought I read sopmeplace if you shorten the pipe & pull the pipe out you get a certain effect to prevent speeding up oe slowing down during the flight.
  John

  Thanks Randy, I looked into my box of PA papers & it said " Engine speeds up during flight? Pull pipe out.
  Thank you, John

I had a similar problem with a  Ro-Jett 50. Increased pipe length helped but what cured it was going to a smaller diameter prop as Randy suggested. I'd give that a try especially if you are running an undercambered prop. They can really put a load on an engine.