I've checked both Underhive (p71) and Gang War (p33), and the weapon is only listed with Gas and Template.the chem thrower both have gas and toxic as rules
Is there another profile somewhere that also has Toxin? If so, it's probably an error, as Toxin doesn't make sense on this weapon.
Since they had the great idea to separate the advanced rules from the basic rules, you need to check 2 different pages. Here you go:I have been trying to find some text in the rulesbook that sais when you should make the injury roll and when you should just subtract a wound
Underhive p53:
3. INFLICT DAMAGE
The target's Wounds characteristic is reduced by the attacking weapon's Damage value (or by 1 if the attack does not have a Damage value). This reduction lasts for the rest of the battle.
Underhive p61:
lf a fighter's Wounds characteristic is reduced to 0 by an attack, or if an attack lnflicts Damage on a fighter whose Wounds characteristic has already been reduced to 0, the attacking player makes an lnjury roll by rolling a number of lnjury dice equal to the attacking weapon's Damage characteristic
Note that the rules as they are written do a (presumably) poor job at handling multi-wound fighters being wounded by multi-damage attacks (if a W2 fighter is wounded by a D2 attack, they go to 0 wound and roll 2 Injury dice with the rules as written (instead of the expected 1 Injury die)).