Golf 4 Engine Fault Code Explanation - System Too Lean

[GolfAtom]

G'day,

Hooked up VCDS to my daughter's 2003 model 2.0 litre Golf 4 to see why it was consuming around 20 litres/ 100km. Got the following engine codes. I guess the engine ECU is over-compensating for the lean fuel mixture, hence the high fuel consumption. If I disconnect the battery for more than 15 mins, the fuel consumption improves to around 8.5 litres/100km (but then gradually deteriorates until the next battery reset).

What do you think is the cause? Is there a code preset that can be done to fix the fuel mixture fault? Thanks..

Address 01: Engine Labels: 06A-906-018-AQY.lbl
Part No: 06A 906 018 GP
Component: 2.0l R4/2V MOTR AT V01
Coding: 00033
Shop #: WSC 01271
VCID: 76E3F91F52E30AAEB1B-4AE8

2 Faults Found:
16555 - Fuel Trim; Bank 1
P0171 - 35-10 - System Too Lean - Intermittent
17536 - Fuel Trim; Bank 1 (Mult)
P1128 - 35-10 - System too Lean - Intermittent
Readiness: 0000 0000

[Umai Naa!!]

Look for splits in the intake pipe, breather hoses and vacuum hoses.

The O2 sensor(s) are picking up a lean mixture after the air mass sensor.

[vdubmotorworx]

If no air leaks the No1 02 sensor and airmass meters are common on these models...replaced so many....VDUB..

[GolfAtom]

Thanks, guys..much appreciated..