tbca21

hello just purcashed 2.8 v6 03 plate only trouble is the engine light has come on .i had it pluged in and it came up with fault code p0411 saying secondary air injection in suffnicent.i had the ode erarsed and all ok but came back on about 200 mile later,i have read up on the fault code and says it could be vac pipes or purge valve .has anyone had this fault or can help thanks