Yup, BG44K is a good start. New/clean air filter might be a good idea too. 45K is a bit early for the plugs to need replacing, but the 00 has the single-tip platinums that are up for replacement around 60K. With so little miles on that Xterra, I have a feeling it has made a lot of short-haul trips and if the engine hasn't been fully warmed up for many of them, it could leave the plugs a bit fouled. Pull one or two and have a look if you're inclined. If you do a lot of short-haul driving, you can change to a "hotter" plug which will do a better job of keeping itself clean under those conditions.
Brent
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