Opening a plug gap is more likely to cause a misfire, cossies of 500bhp+ were running perfectly fine until coilpack came along, even though coilpack had NOTHING to do with performance!!
Coilpack came about due to cost, and lowering emissions, it does produce a stronger spark, of that's there's no doubt, but it was cheaper to make than a distributor and coil, it's better spark ability was excellent for the ever weakening mixtures forced by legislation.
In short don't assume it will stop a misfire, if it is not caused by a blown out spark due to seriously high boost it may well not do a thing for the misfire.
Personally I wouldn't bother with a L1/6/8 but it's your money, I went emerald K3 ecu, that does coilpack(or conventional) closed loop, or mapped position, which is what I use, unless you do a lot of motorway miles and have a chip/ecu that isn't as good as it could be you will likely not see anything you can measure.
Closed loop can be done on my ecu but when I get 40mpg on a run, not particularly easy there's no need, same as there's no need for closed loop imo.
Since changing from msd chip and L6, idle emissions for example are 0.97% CO, and just awsome the smoothness that comes with it, most adaptable ecu I have used.
My mapper emerald charges a set rate of £280 for mapping regardless of how long it takes, ecu was designed in house, made in house and mapped in house, by the most honest person I know.
tabetha