Have you gotten the plug wire rerouted so it doesn't short out on the o2 sensor wiring?
If not get that done and you will most likely see a change, although if it should be shorting at all times it is in contact with the car running.
Also, you might want to test the plug wires..... I had a 3 month old set go bad on my old 95 Bonneville SLE SC. Had a big misfire and was going to the track. I was away from home for the week so I didn't have my ohm meter or any tools so on a hunch I stopped at NAPA, pulled the plug wires off went in, and they just asked what yr, make, model, engine and gave me a new set. Went back out and put them on the car and immediately I saw increase in throttle response, and no more misfire.
I also suggest you ask if you can exchange for the thicker (8mm Series I vs 7.5mm Series II) plug wires. The SI rears won't have nearly as much slack as the SII'*, but will still fit without being overly short.