Is our closed loop operation is always running too rich? If so, why not offset O2 sensor output with either an in-line resistor or a supply voltage divider circuit (depending on whether you want more or less voltage)? That would fool the ECU into a permanent shift. It wouldn't affect WOT open loop (other than having messed with the trims).

 

Pen I don't see how our cars could pass LEV standards if they were running rich at closed loop. No, the real way to make a fix is to do an open loop tweak. For example, use a relay connected to the TPS sensor which switches in a resistor on the temp sensor to make the ECU think the actual temp is hotter than expected, leaning the mixture out - of course, that might result in a timing retard though :-).

UL