Describe the behaviour under the conditions you noticed
Tell us when response changes, rough running or an engine warning appears. Include the complete EGR-related report and repairs already attempted. Do not assume that a measured power shortfall identifies the failed component.
Scope testing to the question
The workshop can decide whether controller data, other diagnostic checks or an appropriate test are useful. Availability of a rolling road does not mean every fault needs a power run.
Send the details before travelling east
Include the engine, gearbox, drivetrain and existing calibration. If the car is modified, list the hardware. The scope and preparation can then be agreed before a journey from Swansea, Neath or Ammanford.
See how to choose a test and send your running concern.
Mobile Stage 1 and ECU solutions, or workshop chassis dyno tuning