Your failing cause your rear O2's are turned off. Get a tune with the O2's turned on then see if the cats your currently using will throw a CEL or not. If not then you'll pass if you get a CEL then you'll need the MIL eliminators or you could do this.
http://www.brenspeed.com/730-2442.html
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07 GT, Whipple H.O. genII, VMP tune, 471 hp and 473 tq, Mcleod RST, Roush tensioner, Kooks LT's w/catted X, Frpp stingers, 3.73's, MGW, Steeda ultralites, Roush RR03 18x10's, 11.67@119
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