vt commodore fuel problems

[robb_john]

i have a 98 vt commodore executive v6 auto sedan and when i got out on the highway the engine light comes on and it is really bad on fuel??
put it on the computer at the local mechanic and it said it was the oxygen sensors so i changed them but its still happenin.. there is a stage 4 performance chip in it could that be part of the reason ??

[strgas]

chipped and dyno tuned or just chipped ?

[robb_john]

as far as i no just chiped i bought it like it, i live in a small town and the closest bigger town is 22 kms away and im only getting there and back twice on $40fuel