ok, a little cam and turbo knowledge is needed here. to the OP, if you want better boost response, better midrange and better topend, here's what you do... step one, pull the head off the bike and get it ported. i'd normally recommend porting it yourself, but with questions like the one you are asking leads me to believe that may end badly. so, in short, step one is ported head. velocity (for low end torque) is moot, due to the fact that your motor is boosted, if you want low end torque, you need to impact your boost response, ie, how soon/fast/hard your turbo spools. one way would be to get a smaller exhaust side, preferably in conjunction with an anti-surge housing. another way is a ported/polished head, as mentioned above (in conjunction with the turbo, stop thinking n/a boys). the third way is what's called a split duration cam setup. basically, your intake cam has more lift and duration than the exhaust cam. imagine the motor sucking in air (or swallowing, again, turbo not n/a) through a garden hose, then blowing out through a straw. the air going through the straw will be going much faster, imparting more velocity to the turbine, giving you faster spool. another effect from higher exhaust velocity is that more heat is transferred to the turbine. the exhaust gasses will be expanding more violently if they hit the turbine sooner, and will again, spool faster.
so, in closing, ported head, split duration cams, smaller exhaust housing on the turbo, and an antisurge housing on the turbo.
god i love turbos