Stage III refers to the ECU flash and FMIC. Or at least that was Stage III when the work was done.
"...here's a word of advice for those who have been saving their lunch money and patiently waiting for the E92 M3 V8 to come to our shores: If you encounter a 335i with a Dinan badge on the trunk, don't throw down for pink slips. This car is so fast in a straight-line drag that you'll have to hitchhike home." Roundel, April 2008 ||08 E92 335i 6MT / Montego Blue / Dinan Stage III, IC, OC, exhaust and Stage 1 Suspension / Morr VS8