This is part of the intro to the version he plays on 
"His Greatest Hits Vol II". I think
is one of the best versions he plays. Anyway I really 
like it and I hope someone will
the tab. This is just what i've figured out, I hope its
 correct. : )

Wont get too technical on the bends and such, this is 
mostly bare bones... mostly.

... I think it's in Standard down a 1/2, i could be 
wrong but it sounds ok to me.

Legend
  b= bend
  h= hammer on
  v= vibrato
  ~= hold note
  /= slide, slide to note
( )= harmonic, ... ?
 pb= pre-bend
  r= release bend

With Wah slight vibrato on each note more on indicated notes

eb-----------------------------------------------------
Bb-----------------------------------------------------
Gb-----------------------------------------------------
Db-12h14--14--12vvvv-----------------------------------
Ab-12h14---------------14--10-----10vv-----12h14--12vvv
Eb-----------------------------0--------0--------------

e|------|      
B|------|      
G|------|   X2 
D|------|      
A|v-----|      
E|------|      

Theres a small bit I missed in the transition played at
 the end of riff 1 sounds like,

Ab--10----------------| 
Eb------12vv\\\\(0)---| 

Muted a bit i think.

Slight Vibrato on each note (riff 2)

eb-----------------------------------------------------
Bb-----------------------------------------------------
Gb-----------------------------------------------------
Db---------------12------------------------------------
Ab--------12/14------12~~~--10-------------------------
Eb--0~~~~------------------------12vv\\\(0)------------

e|------|     
B|------|     
G|------|     
D|------|  X2 
A|------|     
E|------|     


eb-----------------------------------------------------
Bb-----------------------------------------------------
Gb-----------------------------------------------------
Db---------------12------------------------------------
Ab--------12/14------12~~~//14-10----------------------
Eb--0~~~~-------------------------12vv\\\(0)-----------

e|------|     
B|------|     
G|------|     
D|------|  X2 
A|------|     
E|------|     


eb-----------------------------------------------------
Bb--15b-15b-15b--12--15--15b-15\\\\\-------------------
Gb-----------------------------------------------------
Db-----------------------------------------------------
Ab-----------------------------------------------------
Eb-----------------------------------------------------


                v---v dont release just play bent

eb-----------------------------------------------------
Bb--15b-15b-15b-pb15--12~~~~~~\\\\\--------------------
Gb-----------------------------------------------------
Db-----------------------------------------------------
Ab-----------------------------------------------------
Eb-----------------------------------------------------


Thats pretty much what i've got so far and with my 
talent all I can figure out for now.
riff 2 during his singing (the only one numbered), 
freestyle it for fun idk, have fun
it. Blues is all about feeling right?

Email me * if you have more please, i love this song.