I have noticeable engine/exhaust noise at 2000rpm which drops off sharply at higher or lower revs. This is a problem because the engine is at 2000rpm at 30 in 3rd and 70 in 6th. The car is actually quieter at 70mph in 5th rather than 6th. Anyone else had this problem and anyone resolved it?

Not at all. Almost the opposite even. I find the engine in my CR170 to be almost inaudible at 2000rpm

No engine noise at all at 70mph in 6th and exceptionally quiet at all speeds (compared with E class 220cdi).

I think i'm experiencing similar noise than you have. It is most audible while doing just under 120 km/h. I try to drive around 125 km/h because the noise disappears at this speed. I have DSG so gearbox isn't the problem. It sounds like coming in front of the driver. To the passenger seat you can't hear the noise very well.

Do you think it's the same problem?

Sounds like you have a loose bracket or heatshield. You hit its resonant frequency at around 2000rpm.

If you can reproduce the noise when the car is stationary it should be easy to find. As soon as you touch the part that is vibrating the noise will stop

HTH

I think that my noise is an exhaust resonance rather than a component rattle; it is also clearly audible from the passenger side. The dealer checked for loose bits and found nothing. Unfortunately I can't check it at the moment because it in the bodyshop for accident repairs.....

Is it like a throaty V8 sound?

Mines been doing it for ages now, I suspect one of the rubber pipes somewhere has a small split in it that will probably only show up under pressure, I suspect the large on that goes to the maf and airbox.

I have just had my Octavia vRS with CR170 engine back from it's first service and the car now has a similar vibration to that mentioned through the seat/pedals etc all the way up to 2000-2500 rpm on the move and between 1200-1600rpm when revved stationary. The engine that has been smooth for the last 18500 miles now feels really rough. It has been back to the dealers for a quick once over but although they admitted there is a problem they could'nt find anything wrong. It is now going back for a full inspection on thursday. I have read that other cars with this engine have had similar problems. Any ideas???????

Ask them to check the engine tray/shield.