X5 30d E53 Random Misfire when cruising

[sixness]

My E53 X5 has developed random misfire (like an engine hiccup). It most commonly occurs when cruising at at speeds between 100-120km per hour and seems more likely to occur when the road is slightly uphill and engine under slight load on cruise control. It will misfire several times over a few kms, if you slowdown everything goes back to normal. Sometimes it also occurs when you start out your journey usually at lower speeds, the motor will hiccup half a dozen times then it returns to normal. Sometimes I drive the car and it doesn't happen at all. I think the problem may have only started after the crankshaft sensor was replaced? The car sat in the garage for some time after this occurred so I don't know if it is really is related. It's not throwing any fault codes and is really just annoying while its doing it. On a 100km journey it may only do it 2 or 3 times (have a patch of 4 - 6 misfires all within a couple of minutes). Anyone else every had this issue ?