What is this? (part off TB)

[Rev]

I found this next to a spare throttlebody in the shed... umm, what is it? I don't have one of these on the TB on the car! :?

Perhaps this is the reason it splutters for about a second after putting my foot down and generally runs like shit?

[NachoMan]

I can't remember what it's called, but it's something to do with mixture and throttle I think.
I have one on my car.
Next time you're over, take a look...

[Rev]

Ahaha, well that would explain my A/F ratio problems.