I have post it in Superb section but not reply. I hope I can get some response here...

My Superb 1.8T is facing problem . It started with sudden loss of high end power and it is struggling from 3000RPM up to max of 4000 RPM . From 2500-3000 RPM onwards, I can feel some jerkiness in the engine. And the maximum rpm it can go is around 4000 RPM traveling at 150 km/hr. It seems like the car stuck at higher traveling speed from 120km/hr onwards. And the gear change takes long duration.

For slow driving at around 2000 rpm every thing is fine. There was no error codes or any signals appear.

I sent my car to Skoda workshop for VAG scanning and here is the result:

16684 po300 035

Just to add additional information, mileage is just about 13000 km and seldom drive. Recently i can occasionally hear some sort of whining/grinding sound from undercarriage especially during start up and it sometimes stay for a while and there disappear. Do sure whether this has some relation to the speed problem.

get them to do a compression check it may have dropped a couple of valves, we have had this before where it has shown random cylinder missfire, the coil packs have been replaced, then done a compression check and one cylinder was down, i hope it isnt this cause it will be expensive, hope this helps

Thanks. Other than compression drop, what other possibilities should I look at?

I was informed that the dealer has checked the MAF sensor but not sure whether they have done a test with MAF sensor dismantled. I was informed by them that there is no error signal from MAF.

How about DV failure??

usually if the dump valve is going you will start to hear wierd noises instead of the usual psstt, the dealer can check the maf is working by going into measured values and checking that is is recognising the atmoshepric conditions, i.e when they go wrong they read like your 10000meters up a mountain, the reading should be roughly accurate to how far above sea level you are, they can also check other figures like air going into the engine etc.

the dump valve is relativly cheap to replace bout

Just to inform that my car's problem solved. What they do was just key in some code and reset the ECU, and the power comes back.

Thanks.