[1QuickS]

I'm glad to see I have already provided info regarding drilling the top covers for Zeniths, thank you for providing the link.

Zeniths work well if in good condition and the emission stuff is bypassed. I know of a respected shop in Anaheim where owner & his long time coworker both have Zeniths installed on their 2.5 liter 911s. They have been happy with them for at least 10 years and use them as daily drivers. This is a Porsche all-air-cooled shop that has been wrenching Porsches for 50 years for which I have serviced 19 projects including MFI throttle bodies, Solex 40PI, Zenith 40TIN and Weber IDA3C carbs. They are not the only examples I can think of that are happy with Zeniths on their 911s, especially if the Zeniths are installed on a stock 2.2T.

New PMOs are an option compared to the expense of a full-on mechanical refurbishment but Zeniths tend to have a longer-lived throttle shaft/journal life expectancy for various reasons. They do have some design details that have driven me to stop servicing them and focus only on the Webers.