i recall seeing in e46 forums that a porsche or smth lumbar chamber can be fitted. Its custom but perhaps much less than expensive BMW kit ( which I think is actually one size fits all BMW since e36)
128i Sport 6MT converted to Euro 130i spec, tuned by EVOLVE
In-progress: Evolve tune configuration!!; custom lip, some susp.
"The 1-series is the last car that BMW engineered before the Germans, as a car-making culture, fell out of love with driving." - R&T 2013 135is Review