Yaris/Scion & Vitz :: 2002 Toyota Echo - P0171 Code Thrown While Idle

I have a 2002 Toyota Echo. I just purchases a Creader V code scanner. My car is throwing a P0171 code. The light only comes on at idle or while going under 10 mph.

The data from the reader was:
Trouble Code: P0171
Fuel System sta B1 : CL, using HO2S
Calculated Load: 11.76%
Coolant Temp 188.59 degrees

The Freeze frame data was:
ST Fuel B1: -3.91%
LF Fuel B1: 36.7%
Engine speed: 795.5 RPM
Vehicle speed: 0 mph
Intake Air Temp: 82.4 degrees.

I went back today and ran live feed on the O2 sensors. I'm not sure what STF of O2S: STF means. That was another figure displayed on my code scanner.

The O2S S1 was reading between .04 and about .82. The graph looked pretty normal (I guess) in regards to going up and back down between 0 and 1. I don't know alot about mechanics, but I seen a youtube video of a graph showing it going up and down and what is normal. Mine did that on S1.

O2S S1: STF was: 3.89 and -1.57%

O2S: S2 was a different story. It was between like .58 and .66.

The O2S S2: STF didn't give me a value at all. It just said " --% ". The graph of this was slowly going up but in a small range. It started at like maybe .4 and would go up to say .5. The next wave would be like .45 to .55, then .50 to .60, then .58 to .66 etc. So it was not ranging just between 0 and 1. It had a very tight range that gradually increased upwards.

I built my own smoke machine before testing with the code scanner and I didn't get any smoke coming out of the car except for around the air filter housing where the lid meets the bottom portion. I don't know if it's because I had the air filter wrapped in plastic wrap. Can I have an air leak where the filter cartridge connects that would case a lean code P0171? Maybe I should go try to smoke test again. I did it about 3 weeks ago and I can't recall exactly where I had the smoke going into. I thought I disconnected the PVC hose from the brake booster and plugged it in there. I assume the smoke would get thru the whole system. It took about 2 min before the smoke came out of the filter housing.

The car only sets a lean code at idle or going less than 10mph and I'm coasting in a residential area.

I have an inspection coming up in May and need to get this thing fixed before that. I can't find any other air leak, but I wasn't sure a leak around the filter would cause this and I'm not sure the leak wasn't caused by the plastic wrap.

I'm thinking my only other prob could be fuel related. Fuel filter, fuel pump, clogged injector, or can my O2 sensor be bad and causing this? I've already replaced all spark plugs and coils as well as the PVC valve and cleaned the MAF sensor with the appropriate spray.

The car runs ok. The exhaust seems to smell RICH. Like Gas. I don't think my fuel economy is as good as it use to be. It has dropped from as hi as 42 mpg to between 38 and 40 if I'm lucky.

Back when I was having problems before and realized I had a bad coil, I had tried some injector cleaner. Why the codes were back then, but I had erased them and the car ran fine for about 2 months and the light came back.

My MAF sensor was .14 lbs when I was watching the live data above. I plugged my fuel pressure tester directly into the fuel line coming from the fuel tank and got a reading of between 42 and 44 lbs (car not running, just by trying to turn the engine over). I don't know if that is as accurate (or useful) as having the fuel pressure tester on the car and in line to allow the car to start up and run and watch the tester. I have to wait until my part comes do run the test that way.