1st of all please don't get fooled by people asking for payment or with the reason of it is laggy without UDID!
Here's the trick to install iOS 7
Download iOS 7 .ipsw file from any torrent website
( This link is for Asgr only http://bit.ly/16d8LIN )
The update (iOS 7) will ONLY upgrade your current OS keeping intact ALL the settings THUS making it laggy.
So
Download iOS 6.1.2 (never install 6.1.3 or 6.1.4) (idownloadblog.com)
Take backup of ONLY contacts, save your photos.
RESTORE the iPhone to 6.1.3, CLEAN Install (JUST Install the OS, do not change or fiddle with nething)
Now, Keep holding left shift key and click on check for updates and select the iOS 7, your phone will start updating.
Once done, download & install the apps from iTunes.
Restore contact backup from cloud or any app and photos, music, etc.
And then open settings and change it as per your requirements.
Close all APPS and restart the phone.
It WILL WORK PERFECTLY !
iOS Supported Devices:
iPhone 4, 4S & 5
iPod 5
iPad 3 or later