I learnt and still am learning how to tune these turbo Barra’s via pcm tec . If keep reading the forums and all off the info threads , you will eventually understand it ! But it takes a looong time and possibly motor destroying mistakes that u learn from or near misses . But pcm tec is the way to go ! A tuner basically has a couple of hours to tune a car . In which most will do a good job . But it’s no where near perfect! I flashed my TT must be 30-40 plus times and am now just bout happy with it !
Main thing once you change out your injections . Is first make sure your fuel pressure is 4 bar and you buy quality matched injectors with good data with your high / low slope , offset figures! If you load all this info right in the pcm tec . Rest is only fueling and timing . You will need a wide band fuel gauge or u will blow her up ! Watch your timing via pcm tec Ave spark or knock on your data log .
it’s very scary at first ! Only run 7psi gate first as it’s very forgiving at that boost to a point !
but once learnt and mastered at that boost ! It’s great fun road dynoing ( or a proper dyno if u can get one ?) and turning up the boost as saying to yourself “ this thing is just nuts !”