Barry horn

Hi guys . I've recently bought a 2014 insignia 2.0 cdti It's had engine light on since I've got it . I've replaced the maf today with a brand new bosch one erased the fault code but had come back on . P0101 code . Maf performance in correct Any idea what else it could be please guys . Don't want to throw loads of money at diffo parts . Rather fix the actual problem Cheers