drupal toooo slow on shared server

Hallo,
... drupal is up and running but now, ... tooooo slow.

- I am on a shared server but with a lot of rights (.htaccess, ...).
- Set up my site, but now it's too slow.
- Set the memory up to 32MB. Disabled a lot of modules (that would be nice to have).
- The site has about 3 users now (this should not be the issue).
- Have installed xdevel (and then tuned the queries and indizes)
- have read a lot of tips and tricks
- ... nothing helped, it is tooooo slow

- I have now included a primitive debug time mesurement in the output.
- What I found out is that the loading of modules takes about 3 sec. but ..
- .. the funny thing is that the time for loading a the SAME module differs by 0.01 up to 1 sec. on different requests ;-?

Does anyone out there have some ideas, hints, tips. This will be my last try i give to drupal (I am playing around about 3 month now, and nothing helped to speed up the site) before using .....! frustrated...

If you like to see the issues:
www.evangeliumsgemeinde.at

I have read a lot here in the forum but did not find some answer.
Pleeeeeeeeeeeeeeeeeeeeeeeease help
Thx, Willi