The files you're looking for to adjust the bonus extraction rate through research all start like this regardless of race.
RESEARCHSUBJECT_STRUCTUREWORK_
The phase(Vasari) race only has 1 line of this research type which handles both metal and crystal and they are labeled (in order as they are selectable in-game)
"RESEARCHSUBJECT_STRUCTUREWORK_RESOURCEEXTRACT0" to ""3
The Psi (Advent) have 2 lines of 3 research apiece (1 line for metal, 1 for crystal) they are named as follows
"RESEARCHSUBJECT_STRUCTUREWORK_METALEXTRACTPSI0" to ""2 is for metal
"RESEARCHSUBJECT_STRUCTUREWORK_CRYSTALEXTRACTPSI0" to ""2 is for crystal
Finally, the Tech (TEC) are the same as Psi, only they end in TECH instead of PSI
"RESEARCHSUBJECT_STRUCTUREWORK_METALEXTRACTTECH0" to ""2 is for metal
"RESEARCHSUBJECT_STRUCTUREWORK_CRYSTALEXTRACTTECH0" to ""2 is for crystal
Of course all of these are .entity files found in Gameinfo
