Having had my Airflow snorkel for a while now, I suppose I should add some feedback.
It seems in my case to have increased fuel consumption by about 1 litre/100kms at 100-110 km/h.
There is noticeable wind noise from it at speed.
I spoke to Michael and his comments were that some people get 1 l/100km better, some worse. He also suggested that a free flow air cleaner would improve fuel consumption as the airbox tends to concentrate the air into a small area of the paper filter.
I have a long trip, towing around 1.7 tonnes, coming up from July so I will see how it goes...
Cheers
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