It doesn't have a power valve, it just draws fuel on demand from the secondary boosters through the secondary jets.

Today I drilled the seats to .1094 (7/64"). They were just a hair smaller than 3/32. This almost solved the problem... just a couple little pops near the top end. Then I kicked the fuel pressure up to 7psi, from 6. And all poping went away. It might like another 1/2 lb, but I'm going to get a new guage... I just don't trust this one

Still needs some fine tuning though. Now my idle circuit is a little too rich, so I will have to start over with that. I will probably end up putting a larger jet in the seconaries, so I will take some pictures for you when I remove the air horn to do that.

Thanks for your help