curious about something on these two northstars. the lower picture shows what seems to be material cut away to allow that passage to have access to the airway and the top one does not. Is that area supposed to be cut out to work on a SC3800? or is that for some other reason?

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1986 Fiero GT fastback SC3800 3.4 pulley, LS1 TB
1998 Jeep Grand Cherokee with "big boy" 5.9 motor
1983 Honda Goldwing 1100 Interstate

Correct. That passage is the idle air. The stock Caddy throttle body mount "tower" standing up from the water manifold connects that passage to the main bore. However, the adapter plate to use the 3 bolt throttle on a 3800 *SHOULD* have a channel to make that connection without modifying the throttle body itself.

thanks Will. yes the N* to Gen V adapter i picked up does have the passageway machined into it. Somewhat smaller passage way then cutting out the TB itself but saves me the hassle of cutting my own. whew.