IMHO if it runs solid as-is leave it. I'm sure others can add in but shane told me not to push timing too hard on E85, as at some point you'll get diminishing gains.
Do you have aftermarket cams yet? Might do those instead of pushing your current setup. Remember not to be too greedy either. 16g is the imho the perfect turbo but way up top it leaves a little to be desired after a while. I say rock it as-is, or if you really want to know if more timing will really help, get it on a dyno
