Need help from great experts here !

Hi !
I own a VW TDI car ( called Vento ) with a 4 cylinder MK5 engine.
Its been almost 10 years since I bought it new and absolutely love it.
However, few days back I had sudden engine problem while driving and noticed the glow plug and engine warning sign. So I stopped the car immediately and arranged for towing the car at the VW service station.
VW service station guys did usual computer diagnosis and did not find anything.
Next they checked few things and told me the wires were damaged.
They replaced damaged wires and took the vehicle for road test. After the test, They informed me that car is not picking up speed esp. 1st and 3 rd gear and concluded it was issue with EGR unit. They wanted me to replace EGR unit , which costs hefty amount.
I told them this was common issue after emission software update and that VW should cover it or offer heavy discount. After doing more research, I found that EGR unit could be disabled without affecting engine/performance. This seems to be good option for me, as it would not cost me much and there was no need to wait for new EGR to arrive which would take around 12 days.
So they agreed and disabled EGR unit , only to find that this was not an issue at all when they took road test ! The car still has same pickup issue even after disabling EGR.
Then they suspected its injector issue but after swapping other ones confirmed the injectors are fine. All this has taken a week.
Now they have come back stating its an issue with ECM (ECU) which costs a bomb ! The car can drive upto only 60 kph speed ( 40 mph ).
I suspect that service centre guys are just trying to make money.
( first EGR unit replacement suggested, next injector replacement,...)
My questions are as follows :
1) Wouldn't ECM / ECU problem show up when doing computerised scanning and diagnosis ? ( show some faulty codes )
2) How car I be sure its ECM /ECU problem ?
3) Are there any other checks that can be performed ?
( like example, I saw sometimes ECM hose has a leak which can cause problem,
ECM re-programming /reset can fix issue ,....)
Any help, guidance , advice greatly appreciated.
Thanks !

Not great or an expert, and I am not sure what a MK5 engine is. I assume this is a CJAA CR (common rail engine) 2009.5 to 2014? If it is the older pump duce engine that is a different story.

If you have a 2010 clean diesel CJAA CR engine, that had the emission modification done, it has a 4 year 40,000 mile warranty after emission mod.

Any modification of the emissions system (bypass of EGR for example) will void that warranty. If you don't have a CJAA CR engine or you never got the Mod (too late now) you are out of warranty; It is not an issue to remove EGR except for pollution issues. Let you conscience be your guide... I assume India has loose rules on emissions equipment for cars.... In USA it can be a big no no to do these things. Best case is the car can no longer be licensed for road use. Worst case are fines and/or jail.

Did they scan for codes. There should be a story there. ECU problem? That is a wild guess without proof. I would not keep throwing parts into the car. ECU is expensive even used. Post the scan of your codes....

You should post this in the appropriate section of the forum under the model car you have. Good luck.....

Thanks gmcjetpilot for your reply ! I just saw your message.

I turned out that it was not EGR issue. It was confirmed by service centre that it was ECM issue. They quoted very hefty amount, so I took the car to a local mechanic. Since then , things have affected big time as due to covid courier service and parts procurement has been severely affected.

First the mechanic tried to "repair" ECM through one of the workshops , but that didn't go well ( as they found the issue but could not get the replacement part IC )

Next we were tried searching used car ECM ......and finally searching for quite some time found one that works ! I did a test drive just today and the engine seems to be full of live ! Like it was earlier.

Problem now I am facing is, the ECM belong to higher end model which had ABS, automatic AC ...etc which my car model did not have. Due to this, as per mechanic, the dashboard shows fault in engine

Mechanic is insisting that there is no issue but told him I wouldn't able to drive with a peace of mind if the indicator lights are on !

I LOVE my vw car ....but don't know where this will end.....