Leave it well alone.

A 0.48T34 is one of the best setups you can run on a YB. I personally don't rate using the larger 0.63 ex housing on a T34. For the extra lag it gives there are better turbos out there, but a 0.48T34 peaking at 2 bar and holding 1.7 will give super punchy lag free drive and best of all will be reliable and drivable!