For vent presets (or custom vents) with “alongLine” positionTypes, the X/Y position does not change when set. For that, you need to specify the point1 and point2 (the start and end points of the line).
This is another thing that will be upgraded with version One and One-Half - X/Y offset for line emission types.
As for the VentGroup display objects, the VentGroup itself is not a display object, but rather simply a table. Each vent inside of it, however, has a display group that particles are added to - it’s called “content”. You can get it and change around it if you like:
[lua]
local ventContentGroup=myVentGroup:get(“MyVent”).content
ventContentGroup.xScale, ventContentGroup.yScale=3, 0.1
[/lua]