It allows further fueling up and beyond the OEM intended RPM's. That in it's self will not be a problem at all.
You'll want the exhaust housing best suited to your needs. The smaller housing nets better spool-up at bottom end. The larger will have better top end and reduce EGT if your pulling heavy loads.
Tha transmission type will also play a major role.
EGT is direclt related to the engine fueling along with the style and size of turbo. Fuel is adding heat and the airflow THROUGH the head will cool it.