Help Me! Help Me Please!

[LilBitts15]

Can someone please help me with this??? Okay! So... I have a 2000 gt-s with about 105k on it. The check engine light came on a couple of months ago, and it said that i had random cylinder misfire. I got my friend to change the spark plugs and the dealer to turn the light off. The light came on again yesterday. I took it to Autozone to get the code and here's what the print out said:
Code:P0171
Definition:
Fuel trim bank one condition
Explanation:
The powertrain control module uses the oxygen sensor to calculate the air/fuel ratio of the engine.
The computer has recognized a rich or lean condition on one engine back only.
Probable Causes:
1. If bank one and two codes set together suspect fuel pressure or MAF (Mass Air FLow) Sensor
2. Oxygen sensor defective
3. Ignition misfire-repair
4. Fuel injector problem

The PCM has determined that during testing, the fuel system for bank 1 was too lean. (Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank).

CAN ANYONE TELL ME HOW WHAT'S WRONG? WHERE TO START? HOW TO FIX IT? PLEASE!!!!!!!!!!!!

[2way]

Clean your MAF sensor.
http://www.newcelica.org/forums/showthread.php?t=223916&highlight=cleaning+MAF

http://www.newcelica.org/photopost/data/500/medium/MAF_Pic2.JPG
Cleaners in order of preference:
a) CRC's Mass Air Flow Sensor Cleaner (best stuff, but hard to find)
b) Non-residue, Plastic safe electronics cleaner (CRC also makes one)
c) Non-residue brake cleaner

If you've added an aftermarket intake... it will probably need to be BBmodded. The mod is in the Installs Section.

[h8eternal]

do you have an intake?
maybe you have a loose vacuum hose
this happend to me, one vacuum cap and i havent seen a cel for almost a month

[LilBitts15]

Yea... I have an AEM intake on it. What now????

[ATL-GT]

BB mod...

[2way]

If you've added an aftermarket intake... it will probably need to be BBmodded. The mod is in the Installs Section.
Yea... I have an AEM intake on it. What now????
Clean the MAF, reset the ECM by pulling the EFI fuse in the under hood fuse box or disconnect the battery. After things have readjusted.... if you have & know how to use a voltmeter.... you can check the MAF voltage @ the ECM @ spec. idle for 1.1-1.5V DC to determine if you need to modify the intake.

http://www.newcelica.org/photopost/data/500/MAF_Voltage.JPG (http://www.newcelica.org/photopost/showphoto.php?photo=27392)

[deltaB]

If the Idle volts turn out ok, don't forget random vacuum leaks.
I was able to find mine using a OBDII scanner/logger. You could see the O2 sensors flatline and the fuel trims climb any time the brake pedal was pressed. Yes, leak in the vacuum booster is the problem. Toyota couldn't find it. They probably never pressed the brake while they were looking at the trims. They didn't think beyond the fixes the computer was saying.
I figured out what it was the second day after I has the laptop plugged into the ECU.
dB