I know of about 3-4 ways of monitoring the A/F ratio for a lean or rich condition (obviously, I am more concerned about leaning out). What is the most reliable means of monitoring the a/f ratio, and has an installation write-up been posted for it, whether it be a wideband/narrowband sensor or whatever?

wideband of your choice - they all come with writeups (directions) when you purchase them...

How far downstream does it need to be installed? I have no welding or drilling equipment, so I am thinking I can't do this myself...

I would assume after left and right come together, right after the cat..

Wouldn't the cat throw off the readings?

This is what I was thinking as well. Also, since the Cali-spec for 99 has pre-cats, wouldn't I want a wide-band UPSTREAM of the o2 sensor?

I am also trying to find a controller (SAFC, E-manage, etc)/ wideband sensor combo that is compatible AND will allow for simple replacement of a normal narrowband o2 sensor without the need to weld an additional bung into the exhaust...

I wouldnt' worry about the Cali pre-cat too much. Just put it after the left and right bank meet, and definately before the main Cat.

Bring your ypipe to any decent muffler shop. They shouldn't charge more than $10-$15 to weld in the bung.

Empty or take out the cat! It does not throw any codes on a cali, and knock out the precat too. No codes , just flowing exhaust! Its basically a free up grade. Yes I would think before the cat would be better. I dont have a cat so I wasnt thinkn