Ok, I show my ingnorance. To answer the question, it depends on what engine you have, IE, FADEC/EEC or conventional fuel control unit.
On the older technology engines, if you "firewalled" an engine you ran the risk of over boosting the engine exceeding engine limitations and all the like. You would then have to write up the exceedance and MX would go into their books and look at the exceedances. You could in fact overtemp the engine to the point where it would have to be removed.
On the new technology engines, "theoritically" firewall gives you max epr/n1 for the existing conditions. For example on the P&W 4000, with the eec functioning normally, your max thrust is n1 limited. There is protection for overboosting, over speed and overtemp. As long as nothing was exceeded you don't have to write anything up.
Hope that helps.
