RE: Venturi for .21 engine...?
Winibald,
There are three MVVS venturi needle types available for MVVS engines:
1. The .15 type.
2. The GFRT type (for racing .40-.44).
3. The .49A type.
They don't interchange.
I am afraid you will either have to make your own venturi and needle, or to find suitable products elsewhere.