hey guys ive been aware of this issue for a while now but its only just starting to make my car chew a lot more fuel then regularly (struggling to hit 400km's a tank).
pretty much ive got 3 engine fault codes, ive only found out about these by using my flash tuner to run a DTC scan.
codes are:
-p0171
-p1131
-p1132

now the car is modified, its got a exhaust system done from headers to tip, ba xr6 auto. done about 100 000km's. it's also running on a 95 octane tune. Also the issue only happened after i changed the O2 sensor to one i bought off ebay. i've noticed no performance drop, if anything its gotten a little better also at idle when stationary; every now and then the revs drop and then pick back up again.

now what i've done to try to fix this issue...
-reflashed back to standard
-replaced O2 sensor with one i got from a mates BF xr6
-checked the fuses their all fine

any one got any ideas what it could be?
my next step is to check all vacuum lines

i may have fixed the issue by spraying the s**t out of the MAF sensor (under the throttle body), using carby cleaner.
im gonna let it run for about a week and re-test for fault codes to see if anythings their.