I've read in some older posts that HPTuners can overwrite other ECU flashes if needed. Is this the case for all ECM's that HPTuners is available for? also, what would occur if the read file is re-written to the ECM? would that return the previous tune? would this brick the ECM? would i be able to see the configuration of the previous tune or would i need to merge a factory file for my ECU with the read file that i used to license HPTuners to the ECM with? I have a few folks who have had flashes done but are inquiring about having a full tune through use of HPTuners. Others have purchased used vehicles with tunes which do not pass emissions and would like to return to original. In both situations they would not mind paying the license credits for HPTuners.