If my GT6 ever finishes updating*, I'm tempted to give it a run myself and see what I can manage. I tend to be 2-3 seconds a minute off alien times, so at least I'll be able to give you a rough benchmark of what's possible.
But that's not real helpful, because neither you or I are aliens. The goal should always be to just improve a bit on what your current best is. I find comparing myself to aliens is just depressing, I could technically get there but I've got to do it one little step at a time. I like to aim for improving by about 0.3 seconds a session. You can always find another 0.3, and you can't usually find it by being lucky, you've got to drive better. A bunch of those little improvements adds up, and eventually you'll find that a trick that you learned in one corner can be used in others as well.
So I'll get back to you on a time and further improvements once I've refamiliarised myself with the track. But I think you'll find even more time in your next couple of practise sessions. Just getting used to the new line, refining your braking points, and becoming more comfortable with how the car rides with your new style will gain you a bit more. Then I'll see what more I can contribute to helping you go even faster.
*Been updating for the last three hours. Still 30% to go. I know I haven't played in a while, but yeesh.