спасибо. уже понял это.

вот конечный переделанный вариант:

server {

listen 80;
server_name s2.myninja.ru www.s2.myninja.ru;
access_log /home/user/engine-env/logs/access.log;

location @php {
rewrite ^/(.*)$ /index.php?q=$1 last;
}

location / {
root /home/user/engine-env/projects/s2.myninja.ru;
index index.php;

try_files $uri @php;

location ~ \.php$ {
fastcgi_split_path_info ^(.+\.php)(.*)$;
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME /home/user/engine-env/projects/s2.myninja.ru$fastcgi_script_name;
include fastcgi_params;
fastcgi_param QUERY_STRING $query_string;
fastcgi_param REQUEST_METHOD $request_method;
fastcgi_param CONTENT_TYPE $content_type;
fastcgi_param CONTENT_LENGTH $content_length;
fastcgi_intercept_errors on;
fastcgi_ignore_client_abort off;
fastcgi_connect_timeout 60;
fastcgi_send_timeout 180;
fastcgi_read_timeout 180;
fastcgi_buffer_size 128k;
fastcgi_buffers 2 256k;
fastcgi_busy_buffers_size 256k;
fastcgi_temp_file_write_size 256k;
}

location ~* \.(jpg|jpeg|gif|css|png|js|ico|xml|html|htm|swf)$ {
access_log off;
expires 30d;
add_header Cache-Control public;
}

location ~ \.mp4$ {
mp4;
}

location ~ /\.ht {
deny all;
}

}

location /i/ {
access_log off;
expires 30d;
add_header Cache-Control public;
root /home/user/engine-env/engine;
}

}