1999 Ford Focus acceleration problems

Hi,
I think my focus has a common problem affecting 1999-2000 models in that the engine revs higher when I depress the clutch between gear changes - rather than the revs dropping immediately when the clutch is pressed - they rise then fall. I understand this is a problem with the throttle position sensor.

However, I'm not sure if that has anything to do with this problem.

When I am in 2nd or 3rd gear - and basically floor it - feels like it is holding back until the revs hit about 4,000 then it starts to fly! When I get upto about 70-80mph in 4th/5th it then starts to lose power, no more acceleration, and starts to judder. There is no judder at any other speed which makes me think it is not wheel balance. I haven't tried to accelerate through this - didn't want the car to blow up - but acceleration is very slow and laboured at that speed and the juddering seems to get worse.

No problems starting the car, no problems acclerating away in first.

Any ideas would be greatly recieved.

Dave