Just reading all this and just want to point out a few things.
The L139 pilot was complaining to the organisers of that airshow, as he had been promised a display slot on the Sunday, travelled to Ireland from Spain at his own expense, only to have his slot cancelled and allocated to something else on the Sunday at very short notice, despite having been allowed to practice his routine on the Friday and Saturday, also at his own expense. He was killed a few months later in a crash at another airshow.
The L139, SIAI Marchetti S211, second hand Alpha jets, Aer Macchi jet trainer (can't think of the model number at the moment, 336 maybe?) were all considered as a Fouga replacement, but nothing came of it as we all know.
The PC9 was bought after the Tucano, PZL, Texan II were also looked at to replace the SF260 and Fouga.
The PC9 has its controls rigged to give a jet-like performance at higher speed ranges, using it's TAD system. The 950 SHP PT6 has plenty of grunt for an airframe its size, and as said earlier on is economical in fuel burn compared to true jets.
How much fuel does it burn, if you fly around at max cruise or carry around four full gun/rocket pods, it'll suck fuel and empty the tanks in just over an hour, or you can go easy and just doddle around and the fuel will last 4 and a half hours. With a full load of 516 litres of Jet A1 you can work out yourself the cost of fuel.