Halo 3.. I unlocked all the skulls and last i got the IWHBYD Skull .. but my

[help]

armor is still the same?? anyone? i finally got this IWHBYD Skull and i didn't get a achievement.. i didn't think i was going to but i thought i would unlock some armor which has that helmet in it... i checked my armor and everything is still locked but when i ask online people tell me just make sure you have the skulls.. anyone know why it didn't work for me.. i beat it on normal.. wich is how i got my other skulls

 

[Halo3master]

first the IWHBYD skull has no achievement and you need all the skulls to get the helmet.Just f.y.i not all the skulls have achievements.
To get the Hayabusa Body, unlock 5 Skulls.
To get the Hayabusa Shoulders, unlock 9 Skulls.
To get the Hayabusa Helmet, unlock all of the skulls.
this is a list of all the skull names
Black Eye Skull
Blind Skull
Catch Skull
Cowbell Skull
Famine Skull
Fog Skull
Grunt Birthday Party Skull
Iron Skull
IWHBYD Skull
Mythic Skull
Thunderstorm Skull
Tilt Skull
Tough Luck Skull
check out my source and it will show you how to get all of them.