New engine and trouble at mill.

[paulplom]

I have a 2015 transit custom that I've owned since it was two years old with 20k on the clock.
It has been a disaster since day one. New ignition barrel, new drivers wing, new door hinges, luckily warranty covered.
It's now on 45k and I have a full service at mot and I drop the oil 6 months in between. I bought the older version of the custom as I believed it had the same engine as my 2010 transit trend 140. That was remapped and I did 125k trouble free miles in it.
Since January this van has had £7000 out of my pocket. It needed a gearbox rebulid, clutch and flywheel costing £2k. About 1500 miles later it did the famous holing a piston trick which meant a new engine, turbo, injectors and dpf removal and clean costing £5000.
I've had it back on the road a week and after a fast run this morning, it puffed out a large blue/grey smoke screen for everyone behind me to enjoy. I got to the junction and noticed the engine was hunting and the rev counter needle was bobbing up and down.
My last engine did this about once a month and I'm just wondering wtf is going on. I'm worried incase this engine also pops. Is it the dpf regenerating? Is it normal?
I've been pricing up new vans today at citroen, fiat and renault. It's coming to something when the French are doing it better.
I also think the build quality is shocking. The panel gaps are all over the place and after owning ford vans for thirty years, I've become very disillusioned.
Can anyone put my mind at rest?