Some points to consider -
1. Did you try the overdrive test suggested by Mark in post #4?? Or count your gearshifts as you accelerate?? If you are not getting into 4th gear, that would account for about the difference you are experiencing. Your transmission selector might be out of adjustment, and you are driving around in 3rd all the time.
2. Is your transmission slipping?? That will account for higher revs, but only going uphill.
3. Do you know the vehicle history?? Previous owner might have changed the diff ratios if they were running bigger tyres at some point.
4. Do you have a Scangauge or similar, that you can test your RPM with?? Tacho in dash might be giving a false reading.
This is definitely not an engine problem.
It is a transmission, gearing, or tacho problem.
PK
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