So that's what the rainbows look like; looks like a manic drug effect.
Yeah, if you were just going for the engine there's more than enough gas there already. Once you have the combustion chamber down you could run poo through the lines and eventually hit yottawatt through the power of reality-breaking heat. If you absolutely need more gas you can steal materials and use them in the gas exchange fab in the cold loop. Plasmastone can be bought at QM or in space for Plasma Canns, but again, you should never really need it.
I'm pretty hesitant when it comes to putting more free plasma on the station, honestly.