Setting up Carburettors

Hello all,

This weekend I noticed my S3 2.25 with a Weber 34ICH was popping and farting a bit and struggling to get up to temperature even with its muff (or gimp mask as my missus calls it) done up.

I suspected mixture rather than ignition and indeed the plugs were pretty sooty. As a first measure I turned the scew back in a couple of turns and have been letting it out since. The engine warms up nicely now and it doesn't pop and bang as much but it is a bit down on power....any advice on finding the sweet spot. Is one of the gas analyser things from Halfords worth buying...should I tap a Lambda sensor into the exhaust?

Cheers

Dom

gunson colortune. plugs into spark plug hole and you can see the spark in it. available from halfrauds. tune it so it's bunsen blue in the combustion chamber. perfect for mixture setting.