Car Experts,
My car has a rattle noise while accelating, mechanic said it is not a big safety problem ,but the repair for this air intake manifold will cost around $600. I want to repair it by myself. What I can do to fix it, it is kind of annoying. Thank you very much!

It's not that bad. Loosen the air filter box, Remove the intake hose (spring clamp) from the throttle body. Remove the throttle body bolts (3), let it hang there. From leaning over the pass side fender, pull the large vacuum hose off the intake and start taking the 3 bolts and 2 nuts off the intake manifold to the cyl head.
If you put the car on car ramps to start with, this will be a BIG help. You have one more bolt down there at the bottom back side of the intake. And 1 or 2 more vacuum hoses.
Now you're ready to pull it out. Be gental, it's tight coming out, but doable.
All gaskets come attached to the new maniflod, so don't even worry about them. There's foam packing between the block and intake. Make sure that doesn't get disturbed. (you'll see it when you pull it off)
Good luck and have fun.

... just to add to that, there are 2 (12mm) bolts on the bottom back side. Not one like I mentioned earlier. It will also help if you pull off the plastic cover covering the valve cover. This will give you extra clearance when pulling the manifold off.
The vacuum hose for the brake booster, pull that off at the metal line on the firewall. Install the hose on the new manifold before reinstalling.

These tips are on the house. Happy wrenching and keep the band-aids close by.

Some times the noise goes away, is that still the air intake?

What you driving

Actually I had the same problem. Every time I would push the gas down really hard it would make a rattling noise. All you have to do is take off the filter box and the rest of the air intake off. Then you will be looking into a huge hole which leads to the air intake manifold. In that hole you will see a valve. The valve is usually what is making that noise. So all I did was take some cleaner to it and sprayed it on the valve and it went away. So all you have to do is clean it up. But becareful when turning the car back on because when you do, you need to push the gas all the way down to the floor so that the cleaning spray will shoot back out of the manifold so it won't stay in the engine.