I decided to update this old thread of mine, seems more efficient this way don't you think? I've been getting a rear P0136 O2 sensor cell. The first time I got this cell it was a leak at the manifold to downpipe flange. (It's not leaking now) It often pops up when I use 100 octane. Lately I have to clear the cell every day so I decided to change the plugs and use the stock gap this time. (.040) The pictures show a rich condition .... or it's the meth/100 I use at the track. I couldn't say for sure. However, my wide band tells me the car is running a bit lean. Hum. I marked the plugs in the order they came out just in case I found a problem and checked the gaps. All were at 0.35 except one that was .037. I guess I'd gotten in a hurry on the last one when I gapped them down. The cars running strong and hopefully stronger now. Here's a picture of the plugs.

Les