Interesting side note, I discovered last night that the field projector and the ghost vacuum actually make several more appearances throughout the series - peep the gear on the right hand side of the Ecto in ‘Casting the Runes’:
The ghost vacuum is lying down on its back with the field projector sat behind it. It’s likely they appear in more episodes as part of the Ecto interior background art as well. Also note the ghost trap in the bottom right is based on the concept art version rather the one used throughout the show, and the tank-like thing behind Eduardo’s seat could potentially be the pack/blaster that the Egon & Roland figures came with instead of the standard proton packs.
Good observation there. Stands to reason Egon and Slimer hailed a cab to Coney Island and for the final piece of his ruse, took the Field Projector out of the back of Ecto-1 then headed in. It was only about 6 episodes they cameo in the back of Ecto but Ghost Vacuum more than the Projector because they reused the close up shot of the Trap being taken out and the whole shot of the back of Ecto was inconsistent - sometimes only the packs and throwers were on the left side rack and the right side was bare, sometimes the whole back was left bare, and only a handful of episodes, both cameo on the right side above the Trap. And one episode the Ghost Vacuum was miscolored red instead of green.
-Darkness at Noon, Part 2-just vacuum at ~16:16 mark
-Casting the Runes-both cameo at ~6:39 mark
-Home is Where the Horror Is-just vacuum at ~5:12 mark
-Killjoys-vacuum cameos at ~11:34 mark, Egon uses projector
-The Luck of the Irish-both cameo at ~9:11 mark
-Glutton for Punishment-just vacuum at ~17:09 mark
Agreed, looks like the two circles on the side of the ‘weed killer pump’ pack toy as well as the connector and tube atop it. The toy does have the same thrower Roland, Garrett, and Eduardo use for the series. Based on the shape and the caution stripes, I would speculate it is a similar combo pack as the one in RGB’s “The Treasure of Sierra Tamale” where Egon just completed it and Ray used it, the Sub Compact Ectoplasmic Tesseract - an experimental Proton Pack and Trap all-in-one operated by emitting a containment stream and pulling in the ghost with Psychomagnotheric vacuum created by a reverse in polarity. Though since it was essentially a prototype, Egon didn’t have a chance to fix a bug in it, use it too many times and it overloads. Maybe he did and this pack was a back up to Kylie’s trap.
Hmm, but the toy comes with a trap, too. Or perhaps, the pack doubles as a temporary mini Containment Unit where they can deposit captured ghosts from the Trap into it in a case of multiple trappings being required. Curiously, the toy has one label that reads “Emergency Shutoff.”