Ok so is miscalculated or something because when I took off the hood to up the current I measured and it was running 690mA not 500 like I said earlier. That makes more sense in hindsight. Anyway I replaced the 2.7ohm resistor with the original 1ohm resistor I had on there. There is a 940mV drop across this resistor so now I'm running at 940mA.
Now lets see if I can keep enough CO2 on there?