When the T7 was first introduced I flew on it monthly and always felt very unwell afterwards-splitting headaches general feeling of Malaise. On one trip after mentioning it to the CSD she got me 20 mins on the flight deck where the air was fresh not recirculated. Air in J was a mix of fresha nd recircualted.
Iwas told -informally but from infotmed sources that the early GE 777s had problems with bleed air ( covered up of course) and that this was why I felt ill on the T7 compared to previous trips on 74s and DC10s
With all the publicity now about contaminated bleed air I think that may also have something to do with it .
Anyway to comment more directly on your post-I am sure youare not alone -I am sure the toxic oil mist is one aprt of it and also that the two big fams ona 777 cannot push out as much air as the 4 on a 74 and thus the recircualtion rate isnt as fast
PB