Off the wall, especially since I have a 90 Tracker, I was just exploring the Vitara section and saw this. I have a 2003 Chevy Silverado 1500, Z71, w/ 5.3L V8. I added the MSD ignition coils and the wires...didn't notice anything. No MPG gain/loss, no power difference to be felt (although I THINK it felt a little stronger when I was getting on a freeway onramp and punching it, it seemed to take off better from 4,000RPM and up. But that's a lot of RPM). I'd like to say I noticed a slightly smoother idle, but that could be because I changed out my spark plugs at the same time

And, they were expensive as hell. I'm rather disappointed in my decision to buy them...it was stupid. I use the truck as a daily driver and occasional light-duty towing, if any, and hardly anything offroad I would even consider close to "hardcore."
I think they were way more performance-based than my scenario. I'm sure they work better on high-performance engines and/or people that race their trucks.
Recommendation:
Don't upgrade untill you really need it, it's suprising how far the stock ignition system will go.
James
What he said.