3AM airflow meter vs 5AM?

[milld]

Hi,

Just wondering what's the difference between the 2? Is one better than another? My spare engine has the 3AM on it, but I currently run with the 5AM.

thanks

[Hobbes]

Fundamentally the same and interchangable. 3am labelled Hitachi, 5AM labelled Lucas. I believe same design - both 55mm throats.
The 20AM fitted to 4.6 motors is bigger and flows about 30% more.