I have a 2009 X5 3.0D X-drive with 80k miles. Serviced up to date and in good condition, until now.
Quick history, The engine check light came on Oct 2017 and I took it in for diagnosis and it came back glow plugs or controller failure. I also experienced moments of power loss at standstill but improved after warmup. Glow Plugs makes sense here. The controller was replaced and it seemed better, for only a while.
The engine check light came on again, Now it was the MAF diangosed and replaced. But powerloss was still apparent.
At random times when I accelerate and the car simply doesnt respond, crawls even at full throttle. This is from standstill or coasting at 20-40mph. Making the gearbox change down a gear or into 1st to get the revs to rise or lifting off completely and applying again gets it going again. Once the revs go up pasty 2 000 it wakes up, next throttle application its responding perfectly? Motorway cruise control use is difficult the car stuggles to maintain speed and using my own foot sometimes experience a strong misfire type of effect (powerful jerk) but only for a split second. Fuel economy on motorway oddly good, but in town its taken a beating.
I was getting EGR error codes P0401, I have had the EGR cleaned and put back but the car still has random intermittant powerloss. No codes in the last few days, im waiting actually for 1 so can try to diagnose again.
My guess is that the EGR is sticking open when applying the throttle. This wont produce a code I think, but when its slow to open I will get P0401?
I have read maybe one of the injectors is bad, glow plugs themselves, turbo vacuum. EGR vacuum hose?
Any tips for me to look at? Have taken it to 3 different places and they all say change this and that with out investigating

Thanks