Prestolite used to make some higher resistance ignition cables, not sure if they would make up the difference or not.

As to better MPG. My '99 Rodeo was getting a round 17MPg until I noticed that the A/C compressor was running even with the A/C switch off. For some reason, so long as I keep the vent selector switched to the outside air (as opposed to the recirculate position) the compressor stays off and my milage is now 20MPG for a normal average week of driving.