You have to take the param.sfo from the VPK, and edit it with HexEdit to change the TitleID. Once that is done, and you put it back in the VPK, it should run perfectly.
Ongoing curiosity I am having is how GTA-SA Port can work with VitaCheat, but nothing else can. If it can be found out, so other Homebrew can use it, that would be awesome. Or, another User is trying to do a Cheat Engine for the Vita that has Homebrew Compatibility. The Dev of VitaCheat told me he had no plans for it. So unless someone can talk him into giving up the Source........