I just find out :
1) If you have 2 files : orignal data.pak and modified one ;whatever files u are using and get to latest 2.8.17 then you can not use the other file anymore . I believe acclaim has added some bytes / header .
2) I do a reinstall and compare the file size between the brandnew data.pak with the old modifed one (vac/immortal/ etc..watever ) and they are not the same ! So, if acclaim might know if they do a file size check .... Be careful on the file size of the latest data.pak






