Irontiger, Thanks for bringing that ST .90 posting to the forum. I have several and have not ever been pleased with them. OTOH, the .75s are all sweethearts along with the .60s being good and the .51s are super. The .40 needs a restrictor in the venturi which when they were being built by ST such was supplied in the package. GP kind of did away with such when they took ST over. I make my own and a ST 40 will last for years.
Back to the .90, as I went to your question, and I saw the forum was very old, I started to click it off when I saw the above article stating Lyman Slack as the man to see. Having known Lyman many years ago when we were in the B-47 back in the late '50s, early '60s, I just had to go there. I just printed off his expertise and maybe I can resurect my several .90s.

Lyman Slack is a modeler second to none. He can just breath on an airplane kit and it blossoms into a beautiful work of art. I work and work and someone might ask, "Did you find that in a trash can at the field?" [:@] [:@][&o]

Thanks again for your post and to Johnkap for the link albeit years ago. It still works.