On the sensors I basically cheated, just used the O2 sensor defoulers. At first I used some short straight ones---wasn't enough, still got the CEL. The codes were:
P0133, P1275: Aging of Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Below lower limit
P0153, P1276: Aging of Oxygen Sensor Ahead of Catalytic Converter (Cylinders 4 - 6) - Below Lower Limit
Not sure why the codes are regarding the O2 sensors
ahead of the cats. I would think that by eliminating the first set of cats, codes would be for the sensors
after the cats. (I'm also unsure why there would be, for each cylinder bank, TWO codes that indicate the same condition, ie P0133=P1275, and P0153=P1276.) Anyway, I ordered this:
...and the extra length + the angle seem to have done the trick. It's been at least 100 miles and no CEL so far.
BTW, I did the front motor mount (a Pedro-refurbished one) about 3k miles ago.
The headers were some Turbowerx knockoffs from ebay. As I said earlier, they do seem to be well made, in spite of their affordability.