54 cupra tdi dies

[spamhead]

After brief bouts of spirited thrashing my cupra dies @ junctions and then refuses to start again. A quick spray of fuel additive into the air intake and it starts back up fine. This happens very randomly - 5 times so far this year. I've taken it into wakefield seat + they found no probs but refused to lend me a courtesy car (without charging, hmmm courtesy??) to keep it longer for more checks.
Any ideas/suggestions folks? It's kinda pointless having the cupra if it doesn't fancy a blast!!

 

[Moonlight]

Get it to a rolling road and they will prob be able to give you a diagnosis when under load on the rollers. Then take it back to the stealers with the diagnosis.

 

[BlackFR]

Worth logging the MAF flow rate with VAG-COM to see if its on the blink

 

[sssstew]

did you spray the intake stuff after the MAF sensor in the pipework?