AHHHH! I see.
Weird one this.... In HD you can't Monitor through RTAS plugins without first routing the output of a track through an aux.... or use a TDM plugin; which may be what you're saying....
However! In Pt9 /8/7/Le.... You just slap An rtas plugin on , Podfarm, Sansamp whatever, record enable the track with a lowish playback buffer WITHOUT engaging so called Low latency monitoring (i've not used this in 6 years what a waste of time it is.)and away you go.