That is quite a difference... I wonder about using super soft rear tires or firm fronts to try to balance the car more to your liking if you feel that it has too much steering. I would recommend against lowering steering angle on a track this size and with such tight corners.
At the end of the day I had two cars which have never felt better.....Super cool having a fast time to chase. I actually have ended up using full throw on both cars and just not using it all when I can. On the GT1 I went from 1.5mm offset to 1mm and more worn KS Med slicks in the front.....that was all the car needed and it was really good. I realize that running 75 laps is hugely different from running 20 laps. to make a good time doing 75 laps you have to be super constant and minimize unforced errors....I could make the car go faster but being constantly quick is the ticket.
Cheers,
Jim