RE: Venturi for 061 Wasp
I haven't tried, but since the AP is a Norvel copy/rip-off, a Norvel ventury might drop right in.
16100 on a MAS6x3 sounds a bit low, try a full castor fuel if you don't have done that already. I think mine did close to 17000 rpm on 10%nitro and 20% all castor.
After 40 minutes it should be close to worn out...