well this is a hard question to explain cuz every company class their stage 3 differently ... for example CUSTOM CODE stage 3 is for hybrid turbo only .... and some company dont even have stage 3 they jus do a custom remap ... AMD DO a stage 3 is jus a ECU remap with the addition of a Milltek Exhaust system and Hyflow Cats - to include fitting, performance road test and full diagnostic test.