Str 42, Dex 9, Con 28, Int —, Wis 9, Cha 5 ?
I'd give it a a higher Dex (13?) and lower Con (26?), since peacock worms have lightning reactions but are fragile outside their shells. Upsizing & expanding from my proposed stats in post #916 I suggest:
Colossal Vermin
Hit Dice: 32d8+256 (400 hp)
Initiative: +1
Speed: 0 (immobile)
Armor Class: ?? (-8 size, +2 Dex, +?? natural), touch 4, flat-footed ??
Base Attack: +24/+1
Attack: Tentacle +32 touch (1d4+8 plus poison?) or bite +27 melee (2d6+8)
Full: 8 tentacles +32 touch (1d4+8 plus poison?) and bite +27 melee (2d6+8)
Space/Reach: 30 ft./20 ft. (60 ft. with tentacles)
Special Attacks: chew (2d6+16), improved grab, poison, swallow whole, tentacles
Special Qualities: Armoured tube, accelerated healing, darkvision 60 ft., tremorsense 60 ft., vermin traits
Saves: Fort +26, Dex +19, Will +9
Abilities: Str 42, Dex 13, Con 26, Int —, Wis 9, Cha 5
Advancement: 33-64 HD (Colossal)
I think it will have lots of tentacle attacks with which it grabs its "food particles and sticks them in its mouth to chew & swallow. May only be able to swallow Medium-sized or smaller creatures. The tentacles SA is because I fancy it having up to 8 Attacks of Opportunity with its tentacles, like a Hydra can make one AoO per head with its Combat Reflexes despite it not having very high Dex.
As for AC, I'm divided. Its body may be soft but it uses its tube to protect itself. So it may have quite a high NA, or even armour or DR.