Go back to the basics- stock plugs with the smallest permissible gap, correct timing, 2" exhaust system, freeflow mufflers ( not the glasspacks, will give you a big headache). I use a Simota air cleaner, cleaned out carb ( no pollution control devices), vitara ring/pinion gears ( 5.12) on 32" dueler MTs. Using 33-35" tires will bring performance to near stock levels ( as if on 195x15 tires with stock gearing)
If you are after low cruising speed with max economy, use Toyota 3k carbs, stock gearing, & 205/70/15 tires.