18mph/1000RPM translates to 93.4mph @ 5200 RPM with std. trans.

Go For It!

holding 85mph on flats/windless conditions should be feasible, both my 1.9 
and 2.1 vans (non-Westy) would do this. If you can feel some appreciable 
increase in speed when you mat it while doing 75mph things should be OK 
powerwise.  Driving at +/- 60mph puts the tach and speedo needles vertical 
in the gauges, maybe VAG is trying to tell us something???  Try your tests 
as time to go between 2500 and 4500 rpm in 3rd gear. Reduces the influence 
of windspeed/hills, and is safer, shorter, more consistent test. Two way 
average is best. Get someone else to operate the stopwatch!!
  Tim Smith