A few days ago that I started to notice that in some places had a poor signal, Then I did a test with the iphone my girlfriend at the same place and under the same conditions, I note that her iphone has better signal than mine. Both has been unlocked by the same method (iLiberty+) and has the 1.1.4 firmware. Also I changed the sim's betewin iphones And got the same result.
The only difference between it and mine is that I change the metal cover. I ain't broke anything inside. I just remove the cable antenna and put it again in it place.
This is the better example: