A 1/4 gain sounds ok but maybe set them by ear if you can or a multimeter just so you have some reference points. Hopefully it will sound even better after a retune. Also, now that you have a partially amped system you may find this thread useful http://www.e90post.com/forums/showthread.php?t=709393
Yeah it feels good when you upgrade slowly, makes the whole experience last longer!
Turbo Dynamics Hybrid Turbos, Wagner Intercooler, DPF Delete Pipe with Sports Cat, Ecotune custom map ~ 422bhp & 618ft.lbs