I wonder if it may be the E-Flight motors, I'm using one in a Balst which is the UK version of a Flash so would be very comparable to an Airfoilz foamie in terms of weight etc. When I 1st had it it pulled 185 watts and was great, the other day as it seemed to have no authority put it on a meter and was getting 110 watts. I've re-set my ESC to re-calculate the throttle range and it's almost up to 145 watts but haven't flown it since, the Blast though was never fast with that motor and a 12 x 6 prop but it did have torque and would prop hang / climb vertical easily.
You may want to try just changing the motor first, I've just put a ParkMaster together with a Emax 2215/20 http://www.giantcod.co.uk/product_in...2763fe1887afda they're also available off ebay as and the difference is it really flies with authortity. I think I'll see how the Blast flies with the Throttle range re-set but may well buy one of these as they're so cheap and am getting 200 watts with the same batteries and a 10 x 4.7 slow fly prop.

Anybody know what the E-Flight 450 should give in terms of watts with a 12 x 6 on it as that may be the place to start.