Wish someone would make a dedicated thread explaining what these do lol get the question asked so many times As Rubix said no ECU will Map itself. these ECU's do slightly adjust depending on what Mods you run but only slight. They can be run on a standard set up with hardly any boost, they can be run on a TD04 as well. Id say there best with a 1bar set up with all supporting mods. The main things they do is Remove the fuel cut, remove the 180km speed limit, better acceleration, improve mid range torque and give better top speed etc. I sing about these things all the time. for a quick 5 minute change and no need for mapping they really are brilliant things. It would be a good idea to get the fuelling checked when you put one in but i never did straight away on both my GT's after putting a plug and play in and they were totally fine. But yeah as far as fitting it is concerned, its 2 harnesses out, pull ecu out then 2 harnesses in the plug and play. no mapping needed at all