Bought a used set yesterday. But screen seems like no screen protector at all. The guy said that is nano liquid screen protector. So how do i know whether there is really screen protector applied?

Root it. And flash wanam lite s4 custom kitkat rom. You will feel the difference. I'm happy now.

For me. I will not wait for official Malaysia kitkat. Since now the wanam custom room is stable, then I recommend you try that rom. Now my phone version is 4.4.2 kitkat and I experience smooth ui and overall performance boost a lot. If you don't want custom rom and still wanna stick with 4.3 you can try this method.
Root your phone, go to playstore download Trickster Mod. Launch the app and go to io scheduler and change to deadline. Read ahead buffer size change to 2048. Apply.

Next go to developer settings. Change all animation scale to 0.5x. Tick Force GPU rendering, Enable MSAA 4X and graphic overlay. Reboot phone and you will feel the difference.

I tried the option I mention, no big difference to the battery because before I touch the developer settings, I still gets battery draining from 4.3. Now I running 4.4.2 with developer settings, I don't feel any difference for battery consuming compare to 4.3

And custom rom kitkat has no row scheduler. Only noop, deadline and cfq. So deadline the best among the 3.

Yes. Depends on kernel, but currently on xda sites don't have any kernel that suits the custom kitkat rom yet. Just stock kernel.

Not that one. It should be Disable Hardware Overlays. And of course turn off animation is the best choice, but if you still want some animation, just adjust to 0.5x duration scale.

Additional: go to settings > lock screen> change lock screen effect to ripple or none. As I know the light effect will cause phone to lag when you unlock your phone.

Turn off data traffic when not in use. Disable gps, wifi, blue tooth.

You mean omega rom? I use Wanamlite 4.4.2 very fast and stable.

See attachment below.

1) root 4.3 stock
2) flash latest CWM.
3) flash Wanamlite 4.4.2

Done !

I straight flash from 4.3 no need to flash stock first. If your phone can't boot up ( stuck at Samsung logo) , then only you flash Russian stock 4.4 first.

Downgrade is possible with Odin.

There are many methods for you to downgrade from 4.4 to 4.3.
The best way I use before is boot to CWM > wipe everything( factory reset, cache, dalvik cache and format system). After everything done now your phone will no os installed. So boot to download mode, connect Odin and flash stock 4.3 tar file. Done!

Another method is using ADB side load to push rom into your phone.

The 3rd method I tried is buy a USB otg cable and put your downloaded rom into your pendrive. Connect them to your phone and use TWRP recovery (only TWRP recovery work, CWM won't work).After that in recovery mount USB otg and install the rom through the pendrive.

It's good to see another Wanamlite user.

tried MIUI today on the I9500 GS4. Claimed to be the fastest and smoothest custom rom but still contain some bugs. overall is perfect.

play with stock rom=the end.
play with custom rom=different story

malaysia version not yet available. you can try russian rom if you cant wait for malaysia version kitkat.

Benchmark scores are useless. Real time experience are much important. Overall performance kitkat is better than 4.3 jb