EDS advertise it as 8.1 litres but thats including the catch tanks which you shouldn't measure.
I measured mine and it was 7.7 litres. When I saw the EDS one on its own I was surprised by how small it was in comparason.
A few people have looked into custom intercoolers and they are much cheaper than people think. Alot go for EVO intercoolers or something and 'make' them fit.