Data files for my 1993 roadmaster 5.7 tpi

[Jim_Rockford]

A narrowband O2 reads rich or lean from stoichiometric no matter the fuel. Adding extra ethanol into the fuel when using a gasoline tune should cause the BLM values to go above 128 since the engine would require more fuel to remain at stoichiometric. Same driving condition = same air but the same air requires more ethanol fuel mass then straight gasoline fuel mass.

So yes it should fool the O2 sensor into thinking its lean and tells the ECM it needs to add fuel hence the Rich condition.