I have a 04 XE without supercharger, so far this truck is been real good, except in the mornings when i insert the key in the ignition and turn it to start the engine, before getting to the START position (in the igniton module)i hear this loud whirring noise that only last for like 2 seconds, then the rest of the day i don't hear anything(i have a feeling this is related to the fuel pump)also i feel sometimes a lack of power, i feel the engine running good it's just the feeling i am pulling a trailer behind wich i am not.
Any ideas?

How many miles on your X?. Have you changed your fuel filter? Sounds like the fuel pump.

it only has 3908K, I bought it brand new 6 months ago. as far as i remember i am hearing this noise since 200 miles, but i tough this was nornal.
I guess i am wrong.

I stumbled on this question while surfing the threads. Of course this is just the normal pressurizing of the fuel system on startup after it has been off for a long enough time to depressurize, I.E. overnight or after parked for a while.

Haha you have a 00-04 Xterra. Sometimes a lack of power is normal...its a curse we all bear for having a cool SUV . If you don't have a S/C, and you're feeling a little less-than impressed by the power you're getting, you might want to look at doing an intake/exhaust combo, even if you aren't considering any other mods. Its worth it, and you'll actually be able to pass other vehicles while going up an incline!

Thanks for the info Mojave explorer,does your truck makes the same noise? i have owned a lot of cars and
trucks (nissan ) and i never heard any of them making this noise, anyway , i am taking the truck to the dealer to have them check couple of other issues i have with the xterra, while there i'm going to ask them to check this issue out.
Now for the mods you suggested Rockskier, are they expensive? and is this something you can do yourself? sorry i'm new in all this modification stuf

xcentric- the mods are not difficult. If you have any mechanical ability at all, you can do an intake (I am thinking the K&N, thats one of the most popular and the one that I have installed) in about 30-40 minutes. If you are looking at the K&N, go to eBay...that's where you can usually find the best prices. There is also one for sale on this site in the For Sale forum. I got mine on eBay for $170.

The exhaust on the other hand is more difficult to do. I installed the Calmini cat-back (also on eBay ..gotta love it!), and it required some cutting. I picked it up for $200. If you're not looking to spend that kind of money, then you can probably get a Flowmaster muffler put on by your local muffler shop for around $150.

$400 for these upgrades may sound like a lot of money, but its worth it to get that much more performance out of your Xterra. It's a fun truck, but the lack of power on the 00-04's can get frustrating. Since installing an intake and eshaust, I can actually PASS other cars going uphill now, which is a wonderful thing . PM with questions, or ask. There are some very skilled people on this site, and they are always willing to help.