Power loss. Need rolling road test advice.

[fletch]

Got an on going problem with the power dropping of instantly at 4500rpm when in 4th gear in my V8S. Doesn't happen in gears 1-3, and not gone fast enough yet in 5th.
Just had a service with fuel and air filters being replaced, but alas no solution. Also cleaned air intake valve etc.
Garage can only suggest going to a rolling road for some serious testing, as they say there could be any number of possibilities for the problem and some on board testing is required when hitting that speed.
Can anyone recommend a rolling road who are TVR friendly (near to Beds would be a bonus also), or even better offer some solutions.

Thanks in advance, Fletch

[fletch]

Thanks Pete,

At least my green V8S will have the right company!