Did he check the fuel pressure ?, if this is way to low this would explain a lot, the dark greens 0 280 150 803's can do easy 300bhp, find a new tuner.
I had a set that were just cleaned and were at 80% duty at 300bhp(crank), so on the limit, 500cc injectors @ 3 bar will flow 400bhp comfortably, so would be a better bet, as always nice to have them a little underworked.
tabetha