[Umanist]

My engine light repeatedly resurfaced for 6 months after, and despite the dealer allegedly replacing the EGR ( indicated by the fault code), just days before it was out of warranty (5yr)  . Repeat enquiries about why the light was still coming on failed to get a resolution and so, since the engine ran smoothly I simply replaced fully synthetic C3 oil (&filters)  at regular intervals and really had no idea what else to do. However, the engine , in the last 3 weeks, begun:
(1) unsteady idling.
(2) making rattling noises for 2.3 secs when under load from accelerating through the gears.
(3) generally sounding much noisier at all times and especially pronounced when at idle ( like the typical bus-noise) .

I paid almost £96 to get a main-dealer diagnosis - at a different depot than before. Their report:

(1) Needs turbo hose replacing or clip tightening - to stop seepage of oil from the intercooler pipe down into the engine bay (- which seems to have started after the replacement (allegedly new)  EGR) .
(2) Could need the EGR sorting out with 4 hours labour so £££.
(3) Could be a turbo related issue.
(4) Could be an injector related issue.

A step by step resolution was recommended.

(1) Replacement hose to Turbo area £180. After that see how it goes and bring back for turbo and injector assessment. At which point I realised this was escalating into crazy fees.

I went away and removed the intercooler and hoses and cleaned them out to a pretty good degree.

My question is , will I need to replace the Turbo, due  a bit too much oil getting past its seals into the intercooler? (currently 100.000 miles) and maybe causing other issues??? The fault code always said it was the EGR ( I bought a bluetooth diagnostic to keep my eye on what it was. (I think the dealer just reset it whenever I went because it was back on by the next day !!!).

I am thinking of replacing some injectors because two sound a bit different when I do the EAR 2 INJECTOR screwdriver test.

My engine is definitely not what it was , from  just a few weeks ago, and so I am wondering if it can be returned to its previous behaviour - and without that EGR light issue! Or if it now has a noisy-worn engine as an ongoing life? (The dealer said it was around 8% so within spec - whatever that means?)

I have just done another oil service and also full discs and pads to all 4 wheels.

At the moment it is hindering my job as Private Hire taxi driver - which is a below minimum ( no regulation on self employ status) wage turnover/costs even at a busy period ( I am doing the accounts which came as a shock) . So this kind of obliges a driver to sort out their own repairs since the garage fees are just beyond the average income of such a job as this.

Any expertise most  welcome ...

[Dazzler]

I'm no mechanic but here are a few observations.

I believe the injectors are one of the more expensive components so hopefully they won't need repair. Have you tried running premium Diesel or an injector cleaner to try and clear them?

Does the Turbo whistle like a police siren if you drive with the windows down under load/ usually a turbo issue will result in the turbo getting noisier.

I haven't done it but believe the EGR can be blocked to bypass it. Blocking plate with just a small hole. I don't know the finer details.

Good luck with it. I'm sure some tech heads will be along shortly.

Have you got any correspondence in writing or via email of the fix done shortly before warranty expired? If an issue was documented and a warranty fix approved by Hyundai you may be able to contact them with this apparently related issue/s.

[xiziz]

I don't know much to help the situation. Rough running at load, under 2000 rpm would be the EGR working as intended, but coupled with a loose turbo hose might be starving the engine of oxygen. Probably the old EGR was so full of gunk that the recirculation was limited much like having a blanking plate installed.

A blanking plate might make it go back to the way it was before the EGR was replaced, but it was replaced for a reason, so doubt it would help blocking it off.
The car should be able to run with a functioning EGR, so something else must be affecting it. It does not sound like you have any noises that are typically associated with a broken turbo. Injectors would be a prime suspect for rough running and loud engine noise.

I'm sure one of our resident mechanics will pop their heads and theories in soon enough!

[nzenigma]

It would seem that your dealerships are following a pattern and trending:
 they are expensive, lack experienced and /or intelligent mechanics, are more interested in your wallet than your car.
The EGR is a function that incorporates several components, so when you say it was replaced, I am guessing that a valve was changed ...perhaps  . Find an experienced independent shop.
Dazz is correct, it can be blanked off, the EGR is required to reduce environmental pollution ,but it pollutes air intake and oil.
1) unsteady idling.
(2) making rattling noises for 2.3 secs when under load from accelerating through the gears.
(3) generally sounding much noisier at all times and especially pronounced when at idle ( like the typical bus-noise) .
This sounds like excess fuel through your injectors, how is the consumption? I would start by checking the low pressure valve on your fuel pump. There is also a pressure sensor on the rail, this can fail occasionally.

[nzenigma]

To add with a bit more time:
The hose to the intercooler will normally have a small amount of oil in it because the oil feed to the turbo bearing seeps through. Don't worry unless there is a lot ( pooling oil) Just clamp it up tight. .... What will a new hose do?? 
If it is spilt ( unlikely) you will hear it. If the clamp is too loose the turbo boost will blow it off the intercooler and you will have 10% power.