What is the difference between the MACE 69MM BORED OUT THROTTLE BODY for Holden VS, VT, VX, WH and the one for VY Ecotec L36/L67 Supercharged 3.8L V6?

The main difference lies in the IAC (Idle Air Control) valve port. The VY throttle body has a larger diameter IAC port compared to earlier models. You can fit an early-model throttle body to a VY, but you cannot run a VY throttle body on an earlier model unless you also use a VY IAC control valve, as it has a larger diameter head. If a smaller early-model IAC head is used with a VY throttle body, it may unwind itself and fail.