A fan wont work. it would only limit the flow even more, unless you had an absolutely perfect fluid turbine set up. which, frankly, you cant do. probably, the best way to increase your flames would be to find a nozzle that doesnt aerate the stream as much, thus letting it burn slower.
Also, I finally found those ingnitors. at wal-mart. and I am dissapoint. They dont have any slimline ones, only big monsters. but, they can be hacked pretty easily, so whatever. but it will add to the size of my rig, which is a shame, considering all my components are precision cut to be as small as possible.