Improved Natural Attack does not really help the golem in this form, since the slams deal no damage. One of the save +2 feats, or Toughness, perhaps?
Edit: OK, I've added Great Fortitude.
Small Construct (Living)
Hit Dice: 8d10+16 (60 hp)
Initiative: -2
Speed: 20 ft. (4 squares)
Armor Class: 12 (+1 size, -2 Dex, +3 natural armor), touch 9, flat-footed 12
Base Attack/Grapple: +6/+8
Attack: Slam +9 (0)
Full Attack: 2 slams +9 (0)
Space/Reach: 5 ft./5 ft.
Special Attacks: Berserk, improved grab, smother
Special Qualities: Cannot be flanked, damage reduction 10/bludgeoning, darkvision 60 ft., fast healing 3, immunity to magic, living construct traits, low-light vision, squirming fortification
Saves: Fort +6, Ref +0, Will +2
Abilities: Str 15, Dex 6, Con 14, Int 3, Wis 10, Cha 1
Skills: Listen +7, Spot +8
Feats: Alertness, Great Fortitude, Improved Grapple
Environment: Any
Organization: Solitary or gang (2 - 4)
Challenge Rating: 7
Treasure: None
Alignment: Always neutral
Advancement: 9–16 HD (Small); 17 - 24 HD (Medium)
Level Adjustment: —
A maggot golem does not speak, but understands one language chosen by its creator (often Common).
Combat
Berserk (Ex): When a maggot golem enters combat, there is a cumulative 1% chance each round that its elemental spirit breaks free and the golem goes berserk. The uncontrolled golem goes on a rampage, attacking the nearest living creature or smashing some object smaller than itself if no creature is within reach, then moving on to spread more destruction. The golem’s creator, if within 60 feet, can try to regain control by speaking firmly and persuasively to the golem, which requires a DC 18 Charisma check. It takes 1 minute of inactivity by the golem to reset the golem’s berserk chance to 0%.
Improved Grab (Ex): To use this ability, a maggot golem must hit a Large or smaller opponent with a slam attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can smother its opponent.
Smother (Ex): If the maggot golem successfully grapples a victim for one or more consecutive rounds, the victim is unable to breathe and is subject to suffocation (see Suffocation rules in the DMG).
Cannot be Flanked (Ex): Since it is composed of a mass of countless maggots, a maggot golem cannot be flanked.
Immunity to Magic (Ex): A maggot golem is immune to any spell or spell-like ability that allows spell resistance. In addition, certain spells and effects function differently against the creature, as noted below.
A magical attack that deals fire damage affects the golem normally.
A magical attack that deals cold damage slows a maggot golem (as the slow spell) for 2d6 rounds, with no saving throw.
Summon swarm, insect plague, creeping oom and other similar spells repair 1d10 points of damage per spell level.
Repel vermin cast on the maggot golem deals damage equal to that of a harm spell to it.
Squirming Fortification (Ex): Because of the Maggot Golem's physical makeup and due to the fact that it is made up of hundreds of thousands of individual insects, any critical hit or sneak attack has a 75% chance of being avoided and thus cause only normal damage.