C6 transmission: kickdown question

[KULTULZ]

Make sure you carb spacer is not a source of vacuum leak, even my brand new one was not true, check the gaskets too..

VERY TRUE!

There can be NO VACUUM LEAKS as this will throw any calibration off. Even a bad PCV System will do it. Did you know that any oil leak is also a source of additional outside air being ingested into the engine?

A vacuum gauge here is invaluable and will establish manifold vacuum to properly calibrate the carb to the engine.