correlated delete with "in" and "left outer join"

I'm using postgresl 7.3.2 and have a query that executes very slowly.

There are 2 tables: Item and LogEvent. ItemID (an int4) is the primary key
of Item, and is also a field in LogEvent. Some ItemIDs in LogEvent do not
correspond to ItemIDs in Item, and periodically we need to purge the
non-matching ItemIDs from LogEvent.

The query is:

delete from LogEvent where EventType != 'i' and ItemID in
(select distinct e.ItemID from LogEvent e left outer join Item i
on e.ItemID = i.ItemID where e.EventType != 'i' and i.ItemID is null);

I understand that using "in" is not very efficient.

Is there some other way to write this query without the "in"?