Q:

How do I make Will saves using Intelligence?

I was wondering if there might be a class feature or Feat that would switch Will saves from being based on Wisdom to Intelligence... Or even base Reflex saves off of Intelligence? 
I seem to remember the latter somewhere, but I can't remember where off hand...
I'm trying to reduce MAD... Even at the expense of Feats, or possibly a few levels of a class/prestige class...
I've Googled to the best of my ability to try and find these answers, but apparently my google-foo isn't that impressive lol

A:

The best resource available for this kind of question is Person_Man’s X Stat to Y Bonus, which includes D&D 3.0, D&D 3.5, and Pathfinder.
For Intelligence-to-Will, I see several options:

Factotum 1st, requires inspiration point, adds Int to any save (or several other things). Factotum is a 3.5e class from Dungeonscape, and uses its own unique “inspiration points” to power its abilities, including the 1st-level cunning insight ability that can add your Intelligence bonus to a saving throw. Inspiration points refresh on a per-encounter basis, so you can use that ability pretty frequently, but you only start with 2. Note that factotum in general is a fantastic class for an Int-heavy character with some levels to spare, but multiclassing is really not worth it for a spellcaster. If you take only one level and want more inspiration points, the Font of Inspiration feat can help you out but be ready to burn several feats on it (the inspiration points it grants grows quadratically with the number of times you take it).
Keen Intellect, Int replaces Wis. This feat from Dragon vol. 3181 is probably what you want. Note that if playing in Rokugan (the setting described in Oriental Adventures), it is restricted to members of the Dragon clan and can only be taken at 1st level. If not playing in Rokugan, DM adaptation of the feat’s Clan property will be necessary. In my experience, the most common “adaptation” is to just waive the Dragon clan restriction and allow the feat to be taken by anyone (it has no other prerequisites), at any level; this has never been problematic that I have seen.

Originally a feat called Keen Intellect, doing entirely different things, appeared in Oriental Adventures, which is a 3.0 book. Dragon vol. 318 is where many Oriental Adventures options, including Keen Intellect, were updated for 3.5, making that version the “correct” one.

Nightcloak 7th, adds Int to all saves. This prestige class from the Complete Divine web enhancement is decent enough, advancing divine spellcasting on every level, though the prerequisites are awful. The 7th-level grace of the dark feature is generally unavailable earlier than 12th level overall.

All of these are from D&D 3.5e; Pathfinder does not appear to have any options here specifically for Intelligence. Charisma has a number of them, so it is not as though this is something Pathfinder refuses to do so much as something it just hasn’t done yet.

A:

Dragon #318, in the article "Oriental Adventures Update: Eastern Flavor" (essentially a guide for converting the 3.0 Oriental Adventures sourcebook to 3.5e), on page 38, has the following Ancestor feat:

Keen Intellect [Dragon]
You may use your Intelligence modifier instead of your Wisdom modifier when making Heal, Sense Motive, Spot, or Survival checks. You may also use your Intelligence modifier instead of Wisdom when making a Will saving throw.

This allows you to use your Intelligence for Will saving throws, though the feat is meant to be restricted as in the setting in question it should only be available to members of the Dragon clan.
The Complete Adventurer splatbook, also 3.5e, features a couple of feats that do similar save shuffling: Force of Personality, which allows you to use Charisma for some Will saving throws (prerequisite Cha 13, only applies to [mind-affecting] effects), and Insightful Reflexes, which allows Intelligence for Reflex saves (no prereq).
This is all 3.5e material; I'm not personally aware of feats or features in Pathfinder that do the same thing. Maybe you can persuade your GM to allow the material - they're not the worst offenders for unbalanced feats. Though they are strictly better than the standard save-boosting feat set in core, those feats (Iron Will etc.) are already sub-par choices, so a more powerful alternative doesn't hurt.

