Well Bro, i did not do it before. But i have few friends tried it, i can't really say because one of them blown his 4AGZE piston because of high boost, another one of them (also 4AGZE to 4AGTE) is doing just fine, he is using what we call "kampong" style, no piggy back ECU, no o2 sensor, he just plug in 2 additional fuel injectors to his intake minifold. Boosting at 20psi now, and about to Tapao Evo 7 stock and other cars.
But Recently being "Tapaoed" by Kancil L200 Turbo. Wahaha
To sum up, i think it is pretty realiable if u convert your GZE to Turbo because you already have the low compression pistions and GZE ECU, so there is nothing much to modi.