Hi,
I don't use vsftpd, but a little search on the net (!!!) gives the answer:
vsftpd faq
Especially these 2:
Q) Help! Can I change the port that vsftpd runs on?
A1) Yes. If you are running vsftpd in standalone mode, use the "listen_port"
directive in vsftpd.conf.
A2) Yes. If you are running vsftpd from an inetd or xinetd program, this
becomes an inetd or xinetd problem. You must change the inetd or xinetd
configuration files (perhaps /etc/inetd.conf or /etc/xinetd.d/vsftpd)
Q) Help! Can I restrict vsftpd data connections to a specific range of ports?
A) Yes. See the config settings "pasv_min_port" and "pasv_max_port".