Please Help if you can... 2006 L200 2litre DiD Diesel, just had it serviced & EGR valve replaced as check light was on, dealer carried out Knock software recall/update apparently???, after leaving dealer i could feel a slight instant power shut down on some light load/throttle applications, drove for a week, problem still there, took back to dealer and explained, checked ecu for errors, no faults apparently so technician carried out fuel injector recalibration or something like that?? (what is that all about as would love to know??) Technician told me to drive and see if that cures after some time, well it has replaced that problem instantly with a nasty engine splutter between 2200 - 2500 rpm under light engine load, seems to come and go but can feel it on a daily basis, when it does splutter there is white/blueish smoke from exhaust ( is that unburnt diesel ?), Iam annoyed at dealer as the problem has changed each time they fiddle with ECU, Technician said it could be fuel but i cant see how as problem only appeared since it left it with them and as the problem is repeatable pretty much at those rpm/load sites i stated, has problem related to this knock update carried out??

please help if you can.. iam starting to lose plot with dealer..!!!!