Here's the product I bought on Ebay.http://cgi.ebay.com/ebaymotors/ws/eB...2BSI%26otn%3D4
After reading the install instructions it states it can do both map and o2.Did you try installing it to control both sensors at the same time.Also how many precat o2s do you have?Did you check the I and O wires if you did try to install it on the map,because it's the opposite of o2s adding voltage will lean o2s but adding to the map will cause the ecm to think the motor's under a load condition and will run rich.The unit you bought(if I read correctly )is only capable of adding voltage up to 500mv unless the I and O are reversed.
I see, I miss understood the directions. I did hook both which was a little challenging. Anyhow I have 2 O2 sensors. I major and the other minor. I replaced both and added O2 extenders to both. Anyhow it seems you do know alot on this subject. That's cool cause it's been taking me a while to catch on. I've been doing this hho addiction since late june 08. I have spent some money though. Anyhow, around town I averaged 16-20mpg and hwy 19-20. I took a trip all hwy and recieved 27-28mpg. I thought that was great. But one thing I do like is the extra power and the clean air.
Always Install the o2 efie on the o2S that's before the converter the one after only tells the ecm how the converter is fuctioning.Have you probed the wires to the pre-cat o2 sensor to locate which is the signal wire.I'm not sure how much leaning the 500mv map en. can do,most map sensors work on a 0-5v range.This may help with tuning because using a map en. is more likely to set codes than the o2 efie.I would start with around 200mv on the o2 efie then drive for a few days and see if you have any improvment in mpg,then you can decide to try the map or increase the o2 efie voltage a bit more.Tuning is difficult if you try to go too fast,I know all too well the anxious feeling you get when you're eager to see mpg gains.