That's a common AI tendency, yes. I seem to remember one AI-probably the Terran variant-pursuing yellow techs more than the others, but not to the extent that the player can.
Research treaties are not nearly as valuable as you might think; they only operate off of base research. This means that even if I have 6x39%=234% mining SBs, 40% customization, 20% Technologists, 10% Nano Recorders, all of my planets surrounded by at least 8x24%=192% economy SBs, AND getting the hidden bonus to research on difficulties higher than Tough (for the player), resulting in about 14.1x as much research as base on Suicidal with all of the above, I'm not granting the AI any more from my research treaty than with NO bonuses, NO mining SBs, NO economy SBs-and running on Tough. Not to mention that it only gives them 10% of it-and that their own racial bonuses don't get to apply to it, either.
Actually, no, since the amount of money the AI will pay for a tech that you sell them is based on your relative diplomacy standings (100 to 80 will earn you significantly less than 100 to 40, albeit not linearly), as well as of course how much money they actually have on hand, not having the AIs research diplomacy techs results in you getting MORE, not less, money from them for your techs.
It's actually better to keep the AIs diplomacy value as low as possible, so that you don't need yours to be artificially high. I only have preliminary research on this, and can't access the document in question presently, but from memory ~100 to ~40 was better than ~200 to ~120; while it's not a linear function and it doesn't scale precisely (that is, ~100 to ~40 does not equal ~200 to ~80), the more diplomacy the AI has, the more you'll need to negate it.
There is not an MV legal way to do any changes with regards to techs. The couple of mods that have been designed to fix the TA AIs problems with techs are NOT MV legal, as good as they may be.
I seem to remember that in DA the ResearchAdvantage line didn't even work, but I can't say for sure. Nor do I know if it would trip a cheat flag.
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Apologies for not being able to offer specific help for the Yor; haven't played in quite some time as my home computer is down, and haven't played TA in even longer.
