Tightened my Exhaust.... Now Car runs different

[crunchie12268]

All right, I was under my car and tightened up a couple of bolts that were loose. It was obvious I had a small exhaust leak cuz there was black smudge all around it. So I tighten a really loose bolt and get everything sealed up. I turned on the car and it a noticably deeper sound and it revved up cleaner.

Here is my question, ever since then I have been driving it and it feels like it had more power in third, which it nice, but I didn't think a little exhaust leak would make that difference. Also, my a/f guage reads two bars into the rich condition, it had never gone this far, it is usually around stoich and will dip into the green when I am on it hard. But now it goes into the green when I am idling and just driving around... it doesn't stay there, but does anybody know what happened? Do I need to bring my Fuel Pressure down some?

 

[90mustangGT]

The exaust leak if it was before the O2 Sensor although usually leaks outwards, between pulses it scavanged outside air which O2 sensor detected and read lean, the computer dumped fuel to compensate, so you were probally running pig rich, now it is right.

That is the thing with computer controlled EFI engines, simple things cause a chain reaction and often one reading means little when considering the whole picture.