Differentiating between the front plugs and the rear plugs should be pretty easy, but it's easier to mix up the two front O2 sensors and the car will run horrible if you mix them up. I mixed them up when I pulled my trans and I ended up having to use the wiring diagram to figure it out...
The fact that it only happens on deceleration leads me to believe that it's an issue in the rear end, like when you unload the drive side of the gear teeth and it loads up on the coast side, something isn't happy. Did you change out the ring and pinion when you had your rear end torn apart? Is...
Is it at all possible you installed the cams opposite their correct side? One of the cams (passenger side?) is a good deal longer than the other to make room for the timing chains. I feel like there'd be some other indication that they're in the wrong head, but it doesn't hurt to check the...