I wouldn't go to a hotter plug. This could possibly screw something up. I'm sure there are resources out there backing this up. Whatever the stock plug gap spec is, run your plugs on the upper spec, as you already know a bigger gap = bigger spark.

IF the stock ignition system is BORDERLINE, you will notice an increase in fuel economy and maybe power if you beef it up with a better coil (Does the XTERRA have a single coil, or does it have distributorless ignition with coils for each wire?) Then you can also run a slightly bigger gap.

The clubs I belong to (Merkur XR4Ti) have found platinum plugs last longer than normal plugs, but their performance level is lower than normal plugs. On our cars normal plugs last 1 year then they start breaking up at high RPM under high boost levels. We opt to run Champion Copper plugs and change them every year. We have also found the MSD-6 systems cause a power LOSS in our cars, but our cars have an extremely strong ignition system that has no trouble producing 650 hp (4 cyl turbo) in one past Ford engineer's Bonneville top speed race car.

How hard is it to change the plugs in the XTERRA? If its easy, I'd stick with normal style plugs (Champion copper, NGK copper) and change them every 1-2 years. They are cheap, and work good.

I'm on this board to learn about XTERRAs, I plan to buy one this summer.

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