EEC-IV and O2 sensor question

The O2 sensors depend on having the right amount of heat to work properly. The further away they are from the heat source, the less efficent they are. With long tube headers, they are often located farther down the tube from the exhaust port than they would be with shorties or stock headers. Therefore they are less efficent in accurately controlling the air/fuel mixture for best economy and minimum emmissions. That doesn't usually hurt the engine, just your wallet when you go the the gas pump.

The Mass Air 5.0 engines had heated O2 sensors, but the heat assist only works for a short time (less than 2 minutes or so) on cold engine startup.

Some guys will use header wrap to hold the heat in, and that helps the O2 sensors. Unfortunately, it doesn't help the headers, since they tend to corrode when wrapped.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.

It's about $20 from Borders.com see http://www.amazon.com/ . Select boo...very good, and I found it to be very helpful.