Plz help with 206 1.4 starting then cuttin out

Hello every1,
I've found this site to b very helpful but I'm still having problems with a s-reg (99) 1.4 206 glx

My sister brought the above car 2 days ago with 120,000 odd miles on the clocks with full Peugeot service history and only just had a new complete new exhaust system and clutch fitted a week b 4 (not by Peugeot)

She test drove the car and it was running fine, drove the car about 40miles home all seemed ok.
Later that same night she went to the local supermarket and when she came back out and went to start the car the car started ran for about 60 secs and conked out, wouldn't start again I've had a look at the car being mechanically minded by the time I got there the car started first turn but was running lumpy if I Rev it above 2000 rpm it seemed to run fine but after a min or 2 the car would cough and splutter and die ! After the car will fire but not start unless left for a while to which it will start and run for a min or 2 then cough splutter and die and so on & so on. I've read up on this site a few poss causes ... Checks done are

.checked connections on ecu/ main relay/ big brown connector under ECU all seemed fine
.replaced spark plugs and coil pack ( made no difference )
.tried replacing battery in key fob ( made no difference )
.tried re setting the bsi system following procedures on here
.checked all fuses in engine bay drivers footwell
.checked all connections on all the sensors eg maf/lumber/throttle position and both temp sensors
.checked fuel pump (seems to prime when ignition on )
.ive tried plugging my diagnostics machine into car (bluepoint microsan 2) but every time I try it fails to communicate with car

Normally no warning light in dash but have noticed the stop sign has came on but since gone off again
Any advice from anyone would be greatly revived as car is still stuck at local supermarket
Thanks for any help Brett