carb problems

[bood]

I have been having some fueling problems lately.

The car on light throttle is giving afr's of 10. when driving to work this morning it really choked up and started to miss fire with alot of black soot out the back, I dropped a gear and got on boost had a little blast and then the car was good as gold off boost afr's were back to 12 - 13 normal driving. I then pulled up at work it was at idle and the afr were really lean in the 16's when normally it's mid 13's

Car is

21 psi
T25
Not sure on jet size but has run lovely the last 18 months

I have ordered a carb refurb kit.
I don't have a spare carb to try either.

Also thanks to GTphil for help via pm

Any ideas or advice welcome. I have read the threads via the search and I think I get the impression it can be a multitude of factors.

[GTphil]

Have you managed to get anywhere with this yet?

[bood]

I had a mad session with carb cleaner and it runs alot nicer thanks. Although I have ordered a refurb kit from Mike which arrived today ready for next weekend.