what?why?how?

Forum: 

Help
hi
can anyone help me with a problem in my grand move (r-reg)
a few weeks back it started racing and after about five mins instead of idling it would rev n dip n rev n dip contantly for about another five mins, i put it down to cold morning starts an maybe the auto choke sticking.
now ive had time to look and listen more closly its not the choke?
not a great car mechanic there are some (lots) of areas in this engin i dont identify with one being the picture enclosed.
if i take off the hose and air fillter box connected to the right of this, i find a hole inside. when i cover the hole with my thumb every thing returnes to normal, ideally i could drive like this and never worrie again however, its inconvienient if i want to change a c.d.
sooooo, can anyone help me with=1. what is this componant.
2.how dose it work.
3.is it the problem
and 4.how do i fix it?
thank you all for any help and advice given.

couldnt get pic on this page goto gallery/cars/what?how?pic.

best regards
jimi