From reading previous posts on this topic, I'd advise a forge diverter valve. This will ensure you hold boost pressure at higher boost levels. The OEM ones are known to break even at standard boost pressure, the revision G's are meant to be better but I think the forge is stinger still.
That would be good for stage 2, however you could add an intercooler to keep intake temps down. Not required but better for power / avoiding heatsoak.