Guitar Effects Usage

What are these Guitar Effects?
On John Mayer’s song Gravity (http://www.youtube.com/watch?v=7VBex8zbDRs if you haven’t heard it) I was wondering all the guitar/amp settings, pedal usage and any other specifics to get the same sound used on his guitar. Thank you kindly!
That’s a good song. The John Mayer sound is all in the hands. Any amplifier with a decent clean channel on conservative settings will do the job but he has two Fender amps (the Blues Jr. is the one he used in the studio the most) as well as a Victoria Bassman clone and a Victoria Reverberato head. I don’t hear any delay or overdrive at all. It’s in his hands and the Fender Strat that he’s most likely playing. I bet he’s playing his John Mayer Signature Model Strat on this track but it could be any number of Strats that he owns including the SRV “Lenny” Strat as well as the Jimi Hendrix Monterrey Pop Strat. The 5-way pickup switch is probably in the middle pickup position for most of the song until he switches it to the middle/bridge position for the solo, thats my guess.
* I failed to list the Two-Rock amps he uses as well as the Gibson L5 guitar which are all possibilities. Make sure you drive the tubes on the amp by cranking the master volume.
* Keep The Blues Alive!
Hot to use Behringer Guitar Link with Guitar Rig 3 Software Edition (Review Sound Testing Overview)