Wasted spark is another gimmick, there masses of much more powerful turbo cars using std coils, although you do get a healthier spark a iggy system in decent order shouldn't have any problem, the problem is the ford coil on the cossie wasn't decent to start with.
I'd fit aftermaket coil first, incidentally coilpack came out due to COST nothing else, it was cheaper to make than a dizzy simple as that, more energy was a sideffect.
MSD blaster 2 coil will transform your car, if it's down to the coil power, easy way to see is close the gaps up, try 0.5mm, this fascination with you can run bigger gaps is you can but don't need to if working perfectly with smaller gap, larger gaps came out due to lean burn engines, as the mix was harder to ignite.
tabetha