Have not done any real science on this, but do know that driving is a much better test of a car than dyno tests. Have been out on empty autobahns with perhaps a total of 15 other Saab turbos, and following some of them, they really let you know when the go to full boost as the black cloud of smoke always appears (you should see the chipped VW and BMW diesels, they use a smoke-screen to hide their escape). My car, as viewd from lots of other Saabs, gives out no smoke of any kind at warp speed acceleration, so combined with plug examinations I don't think it is too rich. Have noticed five hard laps is about all I can take in a morning, and about all the fuel tank is good for.
Most other BMW, Porsche, Audi ect. guys with approx 300hp cars at the Ring report similar consumption if pushed hard on an open/empty track with as stated, constant full on accel or brakes. There is also way more than 1,000 feet of climbing, I think almost 65% of the circuit is steer up or down, so that changes things.
Driving home from Italy late at night at WOT the fuel consumption is much better, seem to remember I can go about an hour and a half on a tank of fuel which is over 200 miles. Will try some more scientific measures this year, driving to Cologne, Stuttgart and Berlin on the weeks before my thre Ring visits. Saab Aeros are at there best on an empty autobahn, effectively no 1993 era stock sedans can keep up. Things have moved on, but a modified Aero can still keep up with most hi-performance cars in the real world on autobahn, but not track, conditions.