Suggestion....

I have used the dmix carb on a few webras - good carb. Works differently, so you want to set the low speed mixture with some care (do not get it rich - the carb works like an accelerator pump)

Leave the pump on, but run the engine without using the pump. Use the muffler/pipe pressure.

Get the engine dialed in close - both high and low speed.

Then hook up the pump.

When running, make small adjustments to the engine. It is probably very close. You will have to lean both needles a little.

But if anything more is required than half a turn either way, adjust the PUMP to deliver the right fuel flow.

Most folks do not adjust the pump to match the engine, and it sometimes delivers too much or too little fuel. Those are the people who tend to give up on the pump.

One one Webra/pump setup (external pump, but still perry) I cut a screw slot into the pump adjust ment hex. Pump was inside of the fuselage, and I was able to adjust it using the screwdriver. Was set up on the bench first, and I could adjust while running. Final tweeks were expected after install, but I never touched it.

Bob