I have been working on my 98 3.0 4x2 ranger for the past year in the search of improving MPG, currently it gets 18 City and 24.5 highway, but used to get 27-29 MPG highway. So, I have owned it for the past 5+ years, had a few issues which caused a misfire, but it was fixed. Now, when trying to narrow down why my MPG is lower then it was 4 years ago, I noticed that when I look at data from the PID from the O2 Bank 1 Sensor 2, it shows a reading of -100 and Voltage reads zero (but all my O2 sensors read 0 volts---do not know why because the bank 1 and 2 are constantly switching), my STFT's are near zero, my LTFT's are about +5% on Bank 1 and +10% on bank 2. FWIW, the truck is a 50 state CA vehicle and do not have any CEL on and I recently reset the KAM (keep alive memory) and it did all drive cycles in less then a day.

Additional info, I smoked my exhaust for leaks and found 2 leaks that I cannot fix since they are located under both catalytic shields (primary ones, not the rear one), the truck has approx 178k. I know some of you would say just drive it the way it is, but I have the time to fix and don't mind as long as it doesn't cost a lot.

Thanks for the help in advance!