Stop postgres writing to pgstat.tmp :: how disable / to verify that postgres statistics are correctly disabled

In the search to speed up the slow generate_tiles.py script (~ 37
tiles per minute) that connects with a postgresql 8.3.5 database on
Mac OS X 10.5.6 installed via macports, I found out with 'iofileb.d' &
'iofile.d' that much disk i/o was used by writing to /global/pgstat.tmp.

Now I disabled statistics (I think) by changing /opt/local/var/db/
postgresql83/defaultdb/postgresql.conf while the postgres daemon was
being stopped:
#track_activities = on
track_activities = off
#track_counts = on
track_counts = off
#update_process_title = on
update_process_title = off

After (re)starting postgres daemon, there is a major speed improvement
(> 575 tiles / minute), but still some statistics writing is being done:
$ sudo iofileb.d
Password:
Tracing... Hit Ctrl-C to end.
^C
   PID CMD              KB FILE
   100 perl              4 ??/webmin/miniserv.pid #webmin
  1030 Python            4 ??/33481/21874.png
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  1025 postgres        168 ??/global/pgstat.tmp

= 124KB for images versus 168KB for postgres in this (short) period of
time.

Questions:
1. How  can I verify that I edited the correct postgresql.conf file,
in other words how can I verify which postgresql.conf file is used by
MacPorts daemon?

I would say by checking the process tree, and check which data
directory is specified:
   103     postgres     /opt/local/lib/postgresql83/bin/postgres -D /opt/
local/var/db/postgresql83/defaultdb
      105     postgres     postgres: writer process
      106     postgres     postgres: wal writer process
      107     postgres     postgres: autovacuum launcher process
      108     postgres     postgres: stats collector process
      259     postgres     postgres: postgres gis [local] idle

2. Is it correct to think that when disabling statistics in
postgresql.conf, no pgstat.tmp should be written to, or are more
actions required?

3. Or should I restart the server machine before these 'disabling
statistics' changes become effective in postgres server?

~Ceriel