Hi Jesper. Homologation form you mention is
https://historicdb.fia.com/sites/def...20_group_a.pdf did not find any evidence of intercooler as you say. Water injection was homologated through extension 09/01 ET valid from 1 Sept '83 together with a new turbo (water injection specific tank capacity 30 litres). What is puzzling is that several extensions have been canceled over the years. May be the intercooler was part of country specific market (like the 530 Bimmer, ius version)? Much later, some japanese homologations showed that the lesson was learned, the intercooler being water sprayed (page 8, extension02/01 WR)
https://historicdb.fia.com/sites/def...52_group_a.pdf