soulseeker6187 already answered above, there is no modem means let say now you using KI1 modem, after you flash it will still be KI1. The current modem will not be replaced that's all.

not all phones will have same performance on same modem, you need to find what modem is best for yourself. im currently still on ki1 modem, since it dont give me wifi/data issues, so too lazy to change/afraid got some problem agn

No idea, i do not monitor batt life but i like KI1 and KG2 as they give me very stable data connection. KI3 and KH3 keep dropping my data. I am on Digi by the way. Also official rom for Malaysia uses KI1 modem.

You can see the line drop H to 3g and gets stuck for awhile before going back to H and loads your page completely. Or the data connection goes away completely and comes back again after awhile.

Apparently just now i went to Samsung Service plaza, they told me they're changing my MOTHERBOARD!

OH NOES!!!! 

guys, the battery will cost me how much?

I have no idea cos i also not yet flash. Both also 2.3.5 and i do not see any diff and I am also lazy to flash. Sticking with KI3 until some good reason comes along.

I am anti KI3 modem. It gives me bad data connection. Have been using KI1 all along and working well. Earlier today just flash KI4 modem so far so good but need more testing.

Guys...

Need advice about to load touch X-POWER+

1. reboot into CWM
2. Wipe Data & Cache (wipe Data only when wanting to make sure everythings gonna work perfekt on non wipe ROM's?)
5. wipe dalvik cache (my latest ROM's does it for you)
4. Flash Touch X-Power [Touch_X-POWER+_XXKI3_2.1.zip]
5. reboot, let it load
6. reboot into CWM
7. Flash SP [Touch_X-POWER+_KG5_1.0_SP1.zip]
8. Wipe dalvik cache
9. Reboot
10. let it load, DONE!

Now im stuck at step 4.

That step. Where do we store those zip file? We load it in CWM? or how?
Have search in his page but not able to find the step or i might miss. need advice on how to proceed. thank you in advance.