How to replace the emulsion tubes on a Mk1

[FJRandy]

Hello people, Randy here from the US.
A couple questions....Is the imulsion tube something that wears out, or was this replacement an aftermarket upgrade?
I've got a '92 3VD, and the carbs are starting to idle rough. I cleaned the pilot jets and it got (somewhat) better, but it's still popping and spitting at idle.
Will replacing the emulsion tubes restore performance, or is this just a precautionary thing? I've owned the bike for a few years now, but I'm just now getting to do some maintainence on it.
Also, what is the "official" name of the part on the microfiche? Part # would really help.

Any info on what to replace/adjust would help as well.
Thanks!
Randy