ivansrb

2001 A3 8L with 1.6l 102hp 5-speed Petrol engine.

He was bought with 220.000 and now it have 273.000km. Car was driven and we take a good care of it (regular services, oil, filters changed, changed the exhaust bc it had a leak on old one etc...)
Car was very responsive, it works great it doesnt use too much oil, and just everything worked perfect till september last year...
Since september car started to act weird...
Now after few months driving it with the problem(we were trying to solve it, didnt just drove it with the problem..) which wasnt solved by many electricians and mechanics, im trying to find someone more experienced to help me with this problem, since i dont want to replace this car to any other, because im financialy not able and this car is so good..

So, Main problems that are happening to my car at the moment is:

- low idle RPMs on the cluster (it says around 200RPM, and before was at 500RPM, sometimes it gets down to like 100 and jumps to 800-900 by itself...)
I think that the cluster is not calibrated and i feel like the speed of the car isnt the same as the speed on cluster.. I think cluster is showing lower number than it needs.
As example I drove it today in 5th gear 90kph and it was @3000RPM, and i think before @3000RPM i was going like 110kph or maybe a bit more...
All other things on the cluster are working okay(clock, kilometers etc.), also it always shows that the tank is empty and i have a constant check engine light turned on.

- Car is shaking when gas is pressed when engine is cold - So main problem is this one, when i drive it when its cold, if i want to overtake someone in second or third gear( i dont slam it to 6k RPM because the engine is cold, i push it max to like 3000RPM) it start to wobble and like lose the power for like half of second, and that happens multiple times while the gas is pressed, it feels just like shaking or like air in the system i dont really know how to explain. Car normaly accelerates but it has that glitching feeling and whole car shakes few times.. I think this stuff can happen since the engine is cold, but it cant be every time when i drive it cold and every time when i accelerate it, because i know that before this all things happened, you could drive it normally even when its cold, press the gas and it goes smooth..

- Constant RPMs @2200-3000RPM - So this is the last and most painfull problem for me.. When the engine is warm and at 90 degrees of course it needs to go, when you press the gas it just needs to accelerate without anything shaking.. My problem is that sometimes it happens the same things like when the egine is cold( it shakes when accelerating) and also if im on highway driving in 5th gear, or 4th or any gear at any speed but anywhere between 2200-3000RPM and u keep it at those RPMS it just shakes while drivinig.. If i drive at 1500RPM it accelerates normally till 2200 and then from 2200 to 3000RPMs it shaking and after 3000 it starts to work smooth again...

We have tried to OBD scan it with VCDS and another one program/device i cant remember the name..
So while scanning we were able to open anything like Climate control, Airbag, ABS ESP, everything instead of CENTRAL ENGINE CONTROL UNIT and CENTRAL ELECTRONICS unit.. I think thats the name.. When we scan it we cant load those units, we tried all but it just not responding and loading..

Cluster is JAEGER and one electrician said that we need to change it (its around 200e)... So basically we cant run diagnostics or remove the Check engine light on cluster because we cant load ECU... And also we cant find whats the failure since we cant load ECU..