Tucson 2.0 SE NAV 2016 Power loss

[cliffox]

After 122,000 miles and no real problems, the engine completly cut out on the motorway last week. RAC rescue eventually and car reporting low fuel pressure.
Local garage found 2 injector seals failed and replaced these and fitted new fuel filter.
Car has always been serviced by main dealer since new and last service was a month before this happened.
Collected car from garage and was running fine, other than strong smell of diesel , which they subsequently tried to clean with pressure wash.
Next day, after around 30 minutes, power seemed really low and turbo not kicking in as usual when accelerating...
Journey home was fine later and car seemed back to normal...
Went for a 3o minute run then back to garage although no power problems at that time.
Next day, after 15 minutes of running normally, power seemed really low again (felt like my old petrol engine when a spart plug had failed and running on just 3 cylinders).
Stopped engine and restarted after a few minutes and all good again...Still a strong smell of diesel...
Same happened today...
Want to take it back to garage but thinking that their diagnostics will say nothing wrong unless the problem is evident when i pull in there... difficult as it will likely be Ok again after switching the engine off and them restarting it...
Thoughts on possible problem welcome....