Wierd thing that happens

[umpkin]

I dont know if this is just my car, or all ca18et's in S12's or common overall, BUT

when i pull up to a junction etc car moving slow or stopped, idle is fine.

if im driving at around 60mph plus, then put my foot on the clutch (i.e coasting) the car wont idle, it just stalls as if i turned off the engine.

i know there is no reason to coast at 60mph but it was more a fluke, i was going along an 'A' road following a merc sports motor, at more than 60 and passed a petrol garage that plod sits at, so i coasted past it so not to gain attention. but the engine just stalled so i tested till i found the speed where it starts to happen. obviously the second i raise the clutch again the engine becomes alive again without a beat.

is this meant to happen, if not what would be the most likely cause???

cheers.