The following works for me, copied from vo-wiki.com and inserted into wgaf.cfg where the aliases are:
alias ttog1 "+turbo 1; alias ttog ttog2; alias acti 'Activate; ttog2'; alias -t ' '; alias mt ttog2; echo 'Turbo ON'"
alias ttog2 "+turbo 0; alias ttog ttog1; alias acti Activate; alias -t mt; alias mt '+turbo 0'; echo 'Turbo OFF'"
alias ttog "ttog1"
alias acti "Activate"
alias +t "+turbo; alias -t mt"
alias -t "mt"
alias mt "+turbo 0"
And farther down where the binds are:
bind Tab +Turbo
-- tsreknor