My Spider Diesel 200 has had a slight intermittent running fault since I've had it (10 months). It is not a big thing, does not last long (typically 5 minutes) and happens about every week or two. The EGR has been swapped to no avail and the car is still under warranty.
The symptoms are booming like one of the back boxes has gone, poor fuel economy (from the instruments) and reduced power. The instruments clearly show that the turbo is less responsive when all this is going on. A typical instrument reading would be (though it can come in at any speed), 30 mph, 1500 rpm, 16 mpg, 0 psi (turbo) on the flat holding steady.
I have always ran super diesel in the 12,000 miles that I've had it. In recent days I have been giving it full throttle runs to the red line (not held) in 2nd or 3rd, but it just happened again.
Otherwise car very good now I've got through the other niggles (nothing re-occuring).