Ya know i once had a problem like this but mine was really a problem as i live in southern california and trying to get from the fast lane to the slow lane isnt very easy as theres typicaly 4-6 lanes to my right, cut right out on me doing 80 a few times and finally after the 3rd time it just wouldnt start so i popped my head under there pulled the hose off the fuel pump and lo and behold the fuel pump intermitinly was failing, sounds like if you havent already done this to get another one and see if your problems continue, if they do take it back but i bet it's the main fuel pump, there really isnt to much else that will just all the sudden cut the engine from whatever speed your doing to 0, i did though once and see if any of this fits your descp because it's also possible these symptoms are being had but not typed in here, was driving down the road one day and hit a bump and the car shutterd alittle but but the engine recovered and kept going, well this got so bad i bould even drive the car every bump would shutter and kill the engine at least until i turned it off and back on, turned out the dist was bad bearings had woren out and the actually dist itself was jumping around on the inside causeing misfires and jacked up timeing.