Only way is to send your .exe to given antivirus author (with .dll, if you got your custom .dll with modifications). They often got special e-mail for 'false positive detection'.
Few years ago I found somewhere on stackoverflow list of all antivirus companies e-mails and instruction how to send it (compress to .7z with password 'password' or something like that, otherwise your e-mail provider will block your outgoing e-mail).
So every update of eloth.net client I had to send just one e-mail with ~50 recipients.
About '2 viruses detected'. Some antivirus software detect virus in official, not modifed Tibia client, so maybe ignore it, if it's antivirus you never heard about.