When I first got my pro tank with the included 2.5 ohm heads, I was happily cranking away at 8.5 - 9 watts. After a week, the head became gunked up so I put in a 1.8 ohm replacement and it tasted burnt. Second 1.8 ohm head started tasting burnt so I lower the wattage all the way down to 7 and now I'm getting decent but not great results. Can the 2.5 ohm heads really handle more watts than the 1.8 or is it just luck of the draw (no pun intended)?