I have to apologize, don't want to come across as bragging... that's probably what it sounded like...
Yes, I agree, the GTR will eat up a near-stock or stock Z on any course with long stretches - assuming equal drivers... PIR road course is a 1.6 mile course based on a short nascar oval... it uses one long nascar straight and two corners, then interior track with many turns. It favors aggressive braking and be daring around concrete and tire walls... Ie GTR was probably driving more conservatively... it was before I installed video... my next PIR event isn't until 9/12-13, and I will have video then and will try to line up with any GTRs that are there... you can see video of my last event from miller motorsports here (
TravisJB Track Video) unfortunately no GTR only a lotus exige on race tires to watch... lotus got around me after 4 laps on my tail, after my engine cut out due to disconnected o2 sensor