It is possible to beat the flamethrower boss without the grenade pistol.
(You'll need to resort to this on Scavenger Mode, unless you want to use riots) Save ALL your 9mm hydras.
Get Necrosis level 2.(at least) Attach some heal items and only use your PE for Necrosis. Start by casting Necrosis then just keep shooting him. When the Necrosis wears off,(He isn't purple anymore) cast it again.
Repeat Repeat Repeat...You may want some MP Boosts in your attachments too. Be sure to have more than just hydras in case you run out of ammo.
(I had 300 and ran out of ammo) Also keep in mind that the necrosis will wear off when his face first turns bloody...no matter how long its been on.(Even one turn...)
We have more cheats and tips for this game here, Parasite Eve 2 cheats
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