I never bought IR 400, but I know that the current version of 400s is Agfa Aviphot pan 200, an aerial film: http://www.agfa.com/docs/sp/aerial/a...4-06-15_en.pdf .
It is sold by Maco under the names Superpan 200 and Universal 200 too. Please keep in mind, that it has only 100 ASA in most developers.

Former versions of 400s was made from other (technical) material.

Aviphot pan works well with a 720 nm IR filter. With the same filter you can use Aviphot Pan 80, a nearly grain free film: http://www.agfa.com/docs/sp/aerial/a...4-06-15_en.pdf .

In comparision to Avi 200 it tends to block highlights which requires some arrangments during development. Avi 200 is well tempered and needs not a special development. It's grain is quite smooth for a 100 ASA film.