alpha worship

hello all 156 devotees i have a156 selespeed and have encountered problems with the g/box just paid out £618 for work .started with hardly any power so had mass air flow meter changed because car computer had set car to run to to it this in turn threw out set up of car allthe way through to cat all the work done now but 4 p1 codes need clearing ,this can only be done at main dealers any help out there