hi guys, noob at winols and ecm, have been using kess v2 to upload pro tuned files to my vehicles and friends cars etc but i have got access to a database with ori and MOD stage 1 - 3 files with full hw/sw numbers attatched. my question is why are some mod files not the correct size of my ori read file? i spoke to a profesional tuner who told me they are possibly part reads of the ecu and to use them i must copy the map differences onto an ori file that i have. Is this correct? if so how is it done? i have basic winols and ecm titanium but i am by no means a pro with these bits of software....

any help would be greatly appreciated!