[Chaplin]

Yes, we are talking about 2 different things.

Jet extensions- From the sumimt catalog- (I bolded the relevant language)

"These Holley main jet extensions feature a new design that actually screws into the metering block. The main metering jet threads into the end of the extension, moving the fuel entry point for the main jet out into the the fuel bowl. When it's in this location, it cannot be uncovered preventing a lean condition during periods of extreme acceleration or braking."

And yes, Holleys have the same problem.

As for the a/f ratio, your dyno sheet should have a line with the a/f mixture right on it. To measure it at home, you need to get an exhaust gas analyzer and stick it in the tail pipe or install an O2 sensor in the pipes and take a reading with that.