very rough idle

I've used the search tool but to no real result.
My 1.8 gti has an idle problem, it sits very low, and recently regularly goes down to 500rpm and has stalled on me, its very lumpy and backfires regularly. I think I.m on the right track when i say it's a mixture problem, but could any of you guys give me a few things i could try/replace to start checking off the list?
Thanks in advance  

BUMP

Also, just a quick question, does anybody know of a mk1 specialist around suffolk that could have a little go at tweaking the engine in order to solve the problem, really starting to grind my gears (not the car gears, the ones in my head)

Right, the first thing to do is check your rotor arm, HT leads and spark plugs.

Make sure that they are working fine and replace if not.

Once you have done that your onto checking the timing marks line up correctly and then making sure the electrical timing is also correct.

Once that is done you need to check the idle screw and get a gas analyser on it (20 quid)

That should sort it out

done the rotor arm, spark plugs etc, done the timing with a strobe, going to have to book it in to get it CO checked i guess, hope this is nothing serious for my little dub

okay, little update: car's all sorted
had to travel to mark at Theberton and get myself a new air mass sensor but got it on, adjusted mixture and all is well.
was considering selling it at one point it was irritating me so much but now my little GTI is running like a dream I don't think I could do it