Oh boy... I can't wait to see all the replies to this one...
The 35 and 40FP have had so many followers, and as many different methods of dealing with the problems, that a person could spend the rest of their life fiddling and never get anywhere.
You could use the stock venturi (the 35FP uses the same size venturi as the smaller one that is shipped with the 40FP), and run the stock muffler, and a 10-6 prop. Set to a 4-2-4 break. After awhile it'll probably take off on a runaway to the tune of 4 second laps and a brite red palm.
After that we tried the 20-25FP venturi, which drops in without any mods. With everything the same it worked pretty good, but still would run away from time to time... 4-2-4 until the runaway...
At some point we started using the Rev-Up 11-4 and 70ft eyelet to eyelet lines to slow down the plane... That didn't last too long, but it worked well while it lasted.
Then we switched to the high rpm low pitch method... Different props, different fuels, different mufflers, head gaskets, tanks, blah blah blah... Still ran away.
I've actually got about 4 of the 40's and 5 35's now, and I never run them anymore. I've phased them out replacing them with Fox 35's, Tigre 46's, and Max-S 35's. My opinion is that the 35 and 40FP have too much power for the size planes they're typically used on... Something larger, like a Magnum might be enough plane to load it down a bit, but why build a plane like that for an FP when there are Tigre 51's? There are better engines out there, that cause less frustration. Finding time and a place to fly is already hard enough, no sense in wasting the occasion fighting with an engine that requires constant tuning. Even when they did run right for months, they'd run away at a contest and blow over the time limit costing pattern points. Short tank it and it dies in the overheads.
Sell it to a collector, or a diehard FP lover... One of my better 35's is on a carrier plane, and does that job ok.