Craig I wouldn't waste your money on fancy sparks for the SC, one of it's main features , it's reliability is encapsulated in the bullet proof but inflexible CIS induction. This afterall is a 'stupid' injection system built when fuel injection was in it's infancy. The engine is a little unresponsive low down but it shouldn't be lumpy, my engine sounds like a silky smooth purring big cat at low revs but then I have practically rebuilt the CIS and renewed all gaskets, seals and o-rings on the engine (what a difference in smoothness).
My understanding of these system s is that they are particularly effective at lower revs which you'd like but above 3000rpm approx their effect is not noticeable as the Bosch coil comes into it's own and the CIS is working at higher throttle openings , valves and cams are syncronised etc. Basically keep your SCs engine in it's powerband above 3000rpm and you'll enjoy the driving experience more. If it's lumpy low down make sure the valves are set correctly, your injectors are clean, you have no induction leaks , the plugs are good and fit a new rotor , distributor cap and fuel filter. If tou have done all that look at mixture strength and timing next. Keep us posted. Also look at this it will give you big bangs for less bucks.
http://forums.pelicanparts.com/showthread.php?s=&threadid=139422
