I took two Ryobis (with the trusty U.S sourced torquey 31cc Ryan engines designed to run multiple implements) to a mower repair shop years ago and asked them to get the best one going with a new carby kit.
One was an old green one from 88 or 89 and the other was a later white bodied one from the 90s and I mentioned to him how I was told that the older ones are better and I reckoned the green one would turn out to be the better unit. When I went back he said I was right about the green one being better as it read 120 psi and the other considerably less.
He re-kitted and tuned the Tillotson carburettor and it has been running strong ever since with my leaf blower attachment. It also makes a handy spare whipper snipper if need be.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!