I've been having two problems with the tremolo of my 2008 am std strat.
The first problem is that its too loose, and when i drop it it whacks the input cable and makes a loud noise, also if I give it one more turn it becomes extrmely stiff and won't even come down.
The other problem is when I'm playing with high levels of gain and I move the bar it makes a noise.
Could it be that they gave me the wrong tremolo arm?

A tremelo arm should not flop around. I would say you are correct about not having the right tremelo arm. I would take it back to where you bought it from and show them the problem. If a new trem arm doesn't fix the problem you should take it to a tech and see what they say.

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2005 Fender American Stratocaster W/Seymour Duncan Hot Rails in bridge and Seymour Duncan SSL-5 in neck.
1995 Fender American Standard Stratocaster
Line 6 Spider II 150 watt head W/Ampeg 4x12 Cab
Laney Pro-Linebacker PL65R

Your arm may not be tight, but it isn't supposed to be. I have heard of people putting a spring in the hole. Personally, I think it might cause damage to the threads if they are too stiff. You can try wrapping your treads on your arm with some teflon tape. It should be just about right.
Another option, you can look at a trem block and arm set from Callaham. It has a delrin lining in the block where the arm threads into that keeps just a little bit of friction on it. And as an bonus, the extra tone and sustain from the block is awesome.

I e-mailed Fender support about this problem and they sent me another tremolo arm, but it didn't solve the problem.
About the springs, why could they damage the threads? Also could someone give me more info about wrapping the tremolo arm threads with tape?

Your guitar should have come with a tiny spring that slots into the trem hole. This stops the arm from going to deep and also causes the play in the arm to stiffen without it being too tight. I'm sure you're local tech would have boxes of these things and this should solve it without having to replace anything for now.

Cheers,
Eddie

Give it a couple wraps with Teflon Tape(Plumbers tape) Should tighten right up. Mike

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The blues ain't nothin but a good man feelin bad.

So the spring won't damage the thread?