What result are you expecting when using suexec?
The default setup via ISPConfig is to restrict use of CGI to the cgi-bin.
To enable cgi in other directories you'll also have to set the options to +ExecCGI for whatever directory.
Suexec enforces the requirements
1/ the script must be owned by the user/group specified by the
SuexecUserGroup directive and have 755 permissions
2/ the containing directory must also be owned by the same user/group.