Found the answer myself, reviewing php files 
Right id topic argument is: $id
So, valid php code:
if ($pun_config['o_announcement'] == '1' && $id == '22' || $id == '27')
1 2013-03-16 16:47
Re: Announcement only in several topics, header.php - How? (valid code?) (1 replies, posted in PunBB 1.2 modifications, plugins and integrations)
2 2013-03-16 15:46
Topic: Announcement only in several topics, header.php - How? (valid code?) (1 replies, posted in PunBB 1.2 modifications, plugins and integrations)
Hello, I want show announcement only in /viewtopic.php?id=22 and /viewtopic.php?id=27.
I should edit header.php, add:
if ($pun_config['o_announcement'] == '1' && [VALID_PHP_CODE]== '22' && [VALID_PHP_CODE]== '27')
[VALID_PHP_CODE] = I tried all the options that I know nothing works.... 
*PunBB 1.2.15
Thank you very much!