ok story short...

I had a downpipe with an o2 bung that dumped right before the oil pan, plugged a wideband in, tuned the sonavabitch and with a different downpipe that ends right under the rack and pinion and recalibrated the lc-1 its reading .4 leaner than my previous tune almost across the board (didnt want to push it any furthur with the readings I was getting). The o2 sensor is 2" from the end of the downpipe, could that be affecting the reading? Should I just retune the whole map?