problems with air mass

[merc_tech]

hi. im having problems with my air mass on my mk6 1.6 zetec. whenever it is plugged in, i dont seem to have any power, but if i run the vehicle with it unplugged, i have power, but its overfuelling, which is a bit of a pain as now the m.o.t is almost due.
any ideas???
please help

[merc_tech]

ive got another cat to stick on it. i took another air mass from another escort 1.6 zetec, although that one would run fone, when on my escort, doesnt seem to work. i am running with a k&n, although it started doing this before i stuck it on. it seems to do it mainly when it is up on engine temp, so im wondering if its actually an o2 problem???

[merc_tech]

hi, its not a heat soak problem. the filter has a constant cold air feed. its really strange. i replaced the plugs and leads today, and now it seems to run fine with the air mass unplugged, although if i plug it back in, the same problem occures-no power. do you think it could be a wiring problem or a fault stored in the ecu???