It is not warping that you have, you are experiencing DTV which happens when the mating faces are not 100% clean or to much run out etc.
As I said before it is a fitment issue.
Delphi pads are not the best, so may be a plan to consider a better brand of pad.
http://www.tomorrowstechnician.com/recognizing-runout-and-disc-thickness-variation-tips-to-decrease-comebacks/
https://www.google.co.uk/search?source=hp&ei=u1oBXLSuKseUa42VvGg&q=What+is+Disc+Thickness+Variation&btnK=Google+Search&oq=What+is+Disc+Thickness+Variation&gs_l=psy-ab.3..0i22i30l2.1372.12234..19797...0.0..0.157.2796.31j1....2..0....1..gws-wiz.....0..0j0i131j0i10j0i22i10i30.oM6iwakAW44