"Losing the metal clips that you're talking of (marked in green on the bottom photos) is the top reason for abnormal Wi-Fi operation after reassembly.
Here are two images, which I shot, that better depict the cause of the issue. Once you lose that piece, you have no option but to order a replacement cover.
In case the images don't work here, here's an external link."
Just cut a washer from the iphone 4 screw kit in the middle and place as you can see on the photo on top the logic board, install the wifi cover than carefully screw the long screw tight so that it contacts with half the washer which contacts the golden pad of the logicboard.
I just took apart my 4S today to replace the screen for the 3rd time and every time I always make sure that the little brass clip is put back by the camera. I'm assuming if apple put it in the that it has something to do with the signal. The metal clip that is on the 4's panel has been remove from the connectors is not there anymore. I believe apple moved that metal clip over to near the camera. I am willing to take it out and see if any changes. After I took it out I didn't see any immediate changes but my router is in the same room. The signal seemed to stay strong thoroughout the house. As for the Bluetooth I was again see no differences in quality of sound or the distance from device to device. Did you make sure the little snap cable that runs from the speaker to the motherboard is connected properly? Sometimes it can be tricky to connect. It connects near the battery connector.
