Will it get an accurate reading if I install it into the HFC bung at the end of the cat that is a couple inches from the dowpipe? I think yes, but I haven't found a clear answer.

 

This is kinda confusing.
You say "at the end of the cat." That means the exhaust flow has gone through the cat, has been scrubbed by the catalist, and this will not give accurate AFR.
Then you say "a couple of inches from the downpipe." A couple of inches from the down pipe is pre-cat and you can get AFR from there.
Which is it?
Basically; before the cat is good after the cat is bad (in your case).

 

Sorry about that wording. I meant to say in the cat assembly pipe towards the front of the pipe closest to the dowpipe and before the actual filtering piece in the middle. (I think that makes sense?) So this should be a fine place then. Thanks.

 

that is the accurate spot...unless you put it on the DP itself...it's up to you...either way...they are both accurate.

 

Good to know. I read that most people do dp, but I already have the bung on the hfc, so that works out well.

 

i have mine at the very end of the dp and it works great

 

just curious what are you using to tune?

 

Were you asking me?

I am not tuning yet. I am trying to troubleshoot power loss/misfire issues. I am data logging with evoscan and mitsulogger. A/F seems about right for the most part, but at misfire I get a lean spike of 16, which I think might be caused by the misfire, but I'm not sure?