This list says 25 total:

http://www.gamefront.com/crysis-3-nanosuit-upgrade-kit-locations-guide/

I just completed the Root of All Evil and found all the kits thus far (12), but there is a remaining 16 points required to unlock the rest of the modules. That's 28 by my count. I thought you were able to unlock all modules? Is my math just horribly wrong?

So far I've unlocked:

Cloak = 3
Energy = 2
Stealth = 1
Assassin = 1
Verticality = 2
Brute = 3

(12)

Still locked:
Endurance = 2
Sensor = 1
Reflex = 2
Deflection = 1
Threat Det = 1
Strength = 3
Weapon Hnd = 1
First Aid = 1
Heavy Armor = 3
Light Armor = 1

(16)

According to the link in the OP there is only 13 kits left. Am I taking crazy pills?

The strange part is on my first playthrough I managed to upgrade everything except for threat detection (1 point), and I scoured the levels looking for the kit I missed but never found it. I deleted my save and started over determined to find them all this time. Obviously my math is off somewhere, because I managed to get one point away from fully upgraded, but now it looks like I would be three points short. The more I think about this the more I'm confusing myself.

I only managed to complete the game with about 5 or 6 things unlocked.

I only managed to complete the game with about 5 or 6 things unlocked.

I want to have all the modules unlocked for my Supersoldier playthrough so I can have maximum versatility.