I had a similar problem with my T25, but I reset the ECU and that seemed to clear it up.

I would suggest you get one of those Gunson fault code readers from Halfords - they're about £25ish. It will plug straight into your diagnostic socket and tell you what fault codes have been recorded - this should hopefully point you in the right direction.

I've used mine so many times now - saved me a fortune.

BTW - when it stalls - does the red immobiliser light on the clock come on? Also - have you checked the wiring on the MAF sensor?