I've had this game for a while, but I've only just noticed this.
The Drengin's main manufacturing and research buildings start out by giving you +25% manufacturing/research and can be ultimately upgraded to give +60%.
For the other races, these buildings start out by giving 15% and can be ultimately upgraded to give 50%.
I haven't been able to find anything about the Drengin tech tree that seems to counteract this advantage, and I've found no other posts about this (for the current version of GalCiv 3, a least) online.
Am I missing something?