My understanding of the 2.0 in the ST is that it is already maxed out (or nearly maxed out) on power as it stands. That is supposedly why the RS is getting a 2.3l...
Last I knew, though a relatively easy fix (and probably ironed out by now), is that the ST was popping the stock head gaskets...
FocusFest 2013: Best of Show
Gateway FFW: Show Class Outstanding
September '13 ROTM