Hi mate sorry to hear it's come back again, not realy sure what to suggest, is yours a cable operated accelerator or fly by wire ?
Easy way to clear codes is to pull the battery negative off then put your foot on the brake pedal for 30 secons or so to discharge any power left in the system and leave the battery disconnected for half hour,
Have a look at the free ssm software on the subaru outback forum, cables can be bought on ebay/amazon and it's loads more powerfull than the handheld scanners, you may get a more detailed description of the fault