Can I gain stage using a low input sensitivity on my i/o to increase signal level and

[brew]

First of all, you can't adjust the cal of the 90io, so I'm not sure what you mean.

Also, even if you could, the mic and preamp are going to have a fixed level of noise. The 90io noise is going to be lower than that. So you're going to get the same result, because the limiting factor is the mic and preamp, not the IO.