ST TDCI - Turbo? EGR? Fuelling?? (This is a long one!)

Hi guys at a bit of a loss at the moment with my Focus.. Not had a proper chance to rip stuff apart lately so looking for opinions before I go belt n braces at it.

Background: (Skip if you're not fussed, could be unrelated..)

Bought about 5 months ago from JCT600 as a lovely runner. Went for a test and was chuffed. Came back to handover and it wouldn't start, initial thoughts were it's the DPF so we all went (Myself, Sales rep and Techie) for a run to clear it out. Crap was coming out the back but the performance was awful and was told go for a long run and see if it helps, should it bot being back next day. Did the run, it was crap brought it back. They had it in and replaced the fuel filter over a couple of days - I'd read the codes that had come up whilst I had it all relating to fuel pressure and as it happens I was friendly with the sales guy, enough for him to be able to inform me that they had misfuelled it before handover. Fast forward after me losing it in  branch and I have full cover warranty for the fuel system and related components etc. But have always had one issue - 1250rpm it often runs like a sack of crap and jerks like hell. I've done alot of reading and seem to have it down to being the EGR but never been certain and again, not yet had chance to strip it down. Add to that, up until around the new year I would also get it not start on occasion after a run, and it'd take a few goes at starting to get it going. (AFTER filter has been done) this hasn't happened this year but the judder does.

Present day: (Any opinions valued!)

Went for a 98 mile round trip and on the very last 5 mins of the trip to my destination i got an error on dash, but no issues. Pulled in, checked all and then restarted and no problems.

Fuelled up and set off back home after about 45mins. About half way back I found a free stretch of motorway to open it up a bit (been sat happy at 67 mph so far all the way there and back to now) and gave it a bit of a run for a mile or two. I got the error on dash 'Engine Service Now' which is what I've been used to seeing when it's not started before.. I lost acceleration  but the car could hold its speed easily enough, dropping gears gave me nothing. Pulled in, had a look, restarted, all good again. Within a few miles of getting going again I got the error again and no performance, but noticed this time (didn't see before) that the turbo wasn't kicking in, it just had nothing on the dials.

I've nursed it back home where I had to turn off whilst parking up to get the other half from work on the way. Fired up again and went home which is a 7 or 8 min mway run, still performance was lacking and no turbo, but no message on screen. I got home and got the readers out and found absolutely nothing in memory, where usually I would see something, everything always seems to clear when the engine is shut off and doesnt store for this sort of issue. I've run it the past few days and seen the turbo can be all over the place, having mostly nothing to holding a steady speed on a flat road it can perk up on the dial or hoover back and feel like the car is dragging. I can't hear anything in terms of bost leak or noise that I would say is different to normal, I've even gone as far as to turn off the sound symposer in ACM to listen better..

The daft thing is, the turbo CAN kick in, and work for no logical reason. I.E. and it decided on a roundabout to give the beans to me as I got a wake up as the wheels had a nice slide going...

What I have noticed is that if I'm on a run now with it being dicky, there is a smell of diesel, and of course plenty of issues with power delivery where the turbo doesnt work..  I have had the covers off and see no leaks on injectors, manifold, fuel lines etc. But despite all this still no codes!

I'm at the minute thinking a boost leak, but I can't find one with a moderate check over all pipes.

Second thoughts would be between either the EGR as I've had the issues at 1250rpm since forever, and not been able to do anything with it up to now; the Turbo, being a variable could it be sticky and if so is it due to EGR (but I don't get how that would cause it to be all over the place no matter what I do); or is I back to it being a fuel delivery issue with pressure from another knackered filter OR a stuffed pump. I'm about to swap out the MAP and intake pipe as a quick thing but don't have time until at least the weekend to be able yo do anything just yet.

Anything isn't a bad answer,  I'm just hasing that many thoughts I'd like to hear other people's as well so I can pick a starting point.

N.b. I have the warranty, but theres already one car in with them at the moment due to a malfunction which was repaired and running, but they're still on with checking more as the sensor that should shut the car off hasn't worked which caused engine failure in the first place. Given the situation, I could take it to them, but they aren't a Ford dealer, and have no kit or knowledge specific to mine. I'm happy to keep it in possession to work this one out myself more for peace of mind, but wouldn't fully trust the warranty work due to how I found out about the last issues. I have a Ford option to go to, but the diags alone and then the cost to actually find the fault in the first place isn't something I would be fully prepared to run with due to alot of things taking my time and resources up at the moment. I've got a contact there that has advised me about this somewhat, but can't give me a fully run down without it being in for a full check over.

I'm capable to repair, have most of the kit needed but just need some thoughts to run with, don't worry about advising me on going back to the dealers etc. I'd rather see what can be done first if I can't do anything beneficial.

Thanks in advance, again all appreciated if you have any ideas.