You can also go down to 0.3mm if you wish, I find mine works best all round at 0.5mm, it may not be a spark problem as in the actual gap, coilpack is not the saviour many think it is, many high power yb's on std type coils, a megablaster 2 for example, more power than a coilpack, for less that 1/3 the price, and 10 minutes to change.
tabetha