it is possible that you coolant temperature sensor has failed and is sending a signal equivilent to cold, which is casuing the computer to run in warm-up mode in which the fuel mixture is enrichened.
It is also possible that the fuel injectors are dirty and not making the proper spray pattern, that can be fixed by a heavy dose of injector cleaner in the gas.
A restrictive exhaust system will casue fuel consumption to increase due to poor exhasut gas scavenging. check the exhasut pipes to see if they have been kincked, perhaps you backed into something and kinked the tailpipe.
