I just installed a new brake pads. But they are making a lot of noise while slowing down. What is the best lubricant/grease to take care of that problem????

1st. There are extremely few places you can use any lubricant or grease in the brake system. In some cases, a very small amount of high temp lubricant on the pins is tolerated but not required. EVO brakes are dual piston so there is less chance of binding.

Ok, there are several things that you don't mention that are important.

You say you installed new pads. Did you do it or have it done?
The stock pads have shims that reduce vibrations and provide some shielding against heat. If you didn't reinstall these shims with the new pads, that can be a source for louder brake noise.

You don't say what type of pads or which brand of pads you installed. That is key info. Some pads are going to shriek, squeal, and grind no matter what you do. Hawk Plus are notorious for brake noise

You don't mention what type of noise either. that is important for determining if it is pad to rotor wear or pad vibration causing the noise. There are a few products called "disc brake quiet" or similar. Typically they are vibration dampers added to the back of the pad. Generally not needed on the EVO. Check out the brakepad thread in the HOW TO section for information on pad types.

Consider posting more information on what is going on

^This.

Yeah i have AXXIS pads with the plastic shims, and they still squeek like crazy. I think some pads just have different meterials causing noise under light breaking.

? I never had issues with my ULTs (also on our GTS). Check your shims and grease. You might want to blow out any dust in the brake calipers.