New ignition will do it, at the cost of several hundred dollars and much adjustment and tweaking, for a grand gain of next to nothing. The A/F densities in a stock RS are not great enough to merit a heavy-duty ignition. Also, what makes you think the stock ignition DOESN'T produce a "long-lasting" spark? Your RS does not have a distributor, thus you already have a lot of the source of the gains you see in ads for MSD, Crane, etc.