mustangchris09

I just got an o/r x pipe on and the car ran fine without the tune i ordered from American Muscle. No idle issues, just check engine light because its off road, and got running to lean on both sides, and i thought by putting on the tune which would turn off the rear O2's causing the too lean issue, and I put the tune on thinking it would solve this problem, and it did solve the check engine light issues, but it still smells like its running lean and when you rev it it comes down to idle extremely SLOW and when it gets to bout 750-800, it continues to drop to like 300 or so, but then revs back up on its own?? i dont get it. THe tune is for o/r midpipe and k&n filter, 3.73's, and 91 octane. I put 93 in it today, but higher octane should not affect a lower octane tune right?? Help please