I am noticing some hesitation and lag.

My Xterra always had a little hesitation (you pop the throttle, and the truck takes a split second to say "What?" before responding).

The power is strong, it just seems like it takes a fraction longer now for the engine to respond to input from my foot.

Any thoughts on what this might be?

Engine is stock, but with a K&N filter.

FWIW, my wife's '07 seems much more responsive from throttle input than my '06.

I noticed that too on mine, I just figured its prob time to clean my K&N is all which is on the the list to do this weekend.

Well, the truck is just over 16,000 miles.

I had the oil changed yesterday, but I balked at having the 15,000-mile servicing done.

I wonder if I should've let them do it?

your truck is an 01' and you only have 16,000 miles??? thats crazy. Mines an 06' and i have 24,000

What the fuck . . . ?

uhhh woops, i was like half asleep when i posted that

fuel filter maybe?

when is it hesitating,Off the line or when your all ready moving.My 06 only pauses when i stomp on it from a stop and the traction control causes a slow initial take off.