Vans has indicated that they follow the Rotax spec found in the 912 installation manual which says:
Exhaust sockets material: X6CrNIMoTi 17 12 2 (DIN 1.4571) (316 stainless steel)
Exhaust elbow X 15 CrNiSi20-12 (DIN 1.4828) (309 stainless steel)
Muffler Material: X 6CrNiTi 189 (DIN 1.4541) (321 stainless steel)
Tailpipe Material: X 5CrNi 189 (DIN 1.4301) (304 stainless steel)
Ball joint (male) Material: X 15CrNiSi 20, 12 (DIN 1.4301) (304 stainless steel)
Exhaust pipe Material: X 15CrNiSi 20, 12 (DIN 1.4301) (304 stainless steel)
I would still check with Vans to be sure for your specific situation...