running issues

i have a 1.3 from a polo gt fitted with a tldm prog. twin choke, and converted to vac type dizzy. this has been in some 4+ yrs running like a dream however recently its been cutting out under load. it idles prefectly, correct co reading. yet when i go out for a blast and give it full bore it cuts out and  i roll to a stop. wait 30 secs and she will restart a run again. i can limp around but open her up and death:-( cleaned the carb out 3 times now and found no dirt, checked timing and that is perfect and it advances with rpm. fuel flow from the pump seems good. new pugs and coil fitted. im stumped!!!