One of my favorite stories happen this Fall when I was tuning my car.
I had another local tuner ask what A/F ratio I'm running at to get 74mpg. I said around 25:1 He didn't believe me and said its impossible, so I had him ride along in my car and watch the A/F LMA-1 readout.
So after about a 20mile trip running at 25:1 to 28:1 A/F he said
"your LMA-1 needs calibration something must be wrong". I told him I just did a free air calibration that morning and it was reading right. He did'nt believe me and ask if we could install my wide-band into his car. I said no problem. So we then took his car for a test drive and it was reading 14.5 at cruising speed. He then said I'll take some fuel away and I'll show you that it will read 25:1 also. Well to make a long story short he couldn't get past 16:1 and the engine started searching and miss firing. LOL
He now won't shut up about how I need to market this and make him a partner.
