AI mod

The TDM-ModPack is highly recommended. It significantly improves the stock races, and adds several new races, without adding any new techs. There is an older version in the Extras folder on the SE IV CD; the most recent version is available at

http://tdm.otaku42.de/

There is also the AI Campaign Mod (AIC), which I have not tried myself. It is designed to improve the AI's performance in solo games. It is available at

http://www.spaceempires.net/home/downloads-details-302-AI_Campaign.html

Several years ago a "Ultimate Mod" was published; it added a huge number of empires, techs, ships...

Does it still exist? Where can I find it?

The Ultimate Mod was created by Hadrian, who has recently rejoined the Space Empires community. For some reason he left the community and wouldn't let anyone have the mod anymore after he left, but now that he's back you might be able to coax it out of him. Ask over at the Shrapnel forums (www.shrapnelcommunity.com); there is a Space Empires section there which I've seen him posting in recently. Of course, since the mod is so old, it might take some work to get it to work with the latest versions of SE4...

If you're looking for other mods which add huge numbers of techs, try the Eclipse Mod or the Masters Mod - the Eclipse Mod is available at www.spaceempires.net and the Masters Mod should be somewhere on the Shrapnel forums...

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Mr. Flibble says...
Game over, boys!

just wasted an hour myself looking for a mod that improves the ai without messing with the rest of the game. Thank you much guys, should have come here first.

It turns out that AIC may not be what you're looking for, because it makes radical changes to the tech tree, incorporating a lot of the Proportions Mod.

capnq

"Good morning, Pooh Bear," said Eeyore gloomily. "If it /is/ a good morning," he said. "Which I doubt," said he.