more info required here matey!
Larger MAF housings are only fitted when a larger turbo is fitted with the ability to max out the stock maf sensor in it's housing.
AGU engines will require the obd II VR6 sensor housing, with either the vr6 or the agu sensor.
ARZ/AUM engines will require the S3/LCR/TT sensor housing. there are also two different version of the sensors on the ko4 cars so check part numbers against your own. easiest thing is to fit your original sensor into the larger housing.
If you are on the stock turbo, or a ko3s on an AGU, the stock housing is fine and shouldnt be changed.
Any change in size of maf housing will require the car to be mapped again specifically taking this into account, as the CSA increase from a 70mm maf to an 80mm maf is a whopping 38%, meaning an 80mm maf on an unmapped car will underfuel by about 38%!
As a side note, if it's an AGU, the old test of unplugging the maf to test it doesn't really work well, as the AGU relies on maf 100% and hardly runs at all without it!
