Installed EFIE without noticing mpg improvement. Issue with partially clogged catalytic converter must be dealt with before any more testing.
My plan was to bypass the Pathfinder's computer O2
sensing using the EFIE so I could try using 99.9% Napthalene mothballs(1 for every 4 gallons) and Bosch Platinum plus 4 sparkplugs. The sparkplugs did allow a 2.5 mpg increase in mileage with the existing plugged catalytic converter. A new converter is in the mail.
1/17/12 Update: Catalytic converter not plugged. Looks like problem may be Throttle Position Sensor as transmission is confused at speeds around 35 mph with mild acceleration. Tinkered with TPS alignment and that solved the transmission issue but gas mileage dropped to 14.25 mpg. Waiting to install new TPS unit now.
5/4/12 Update. Replaced TPS unit and adjusted by trial and error to arrive at sweet spot position. Result is mpg at 21.3 for highway economy. City is 15.4 mpg. Next project is adding a Hycor2A, then HHO