While the other LS runs well (around 1.42-1.44/lap), it pits every 3 laps. I used the Mazda MX-5 Miata LS off the shelf (0 miles, $0 spent (no HP boost oil change)) with no settings changes (ASM/TCS), and still put the other LS at + 1 LAP.
The benefit of this race is both its length, and the fact that the Miata doesn't move that fast (making it easier on to turn, and easier on the tires). I pitted after every 8 completed laps, with the front right tire going red somewhere around the 6th, and all red by the end of the 8th.
I haven't been able to break 1.40 with an off-the-shelf LS, but I think it can be done (maybe not by me). There are, however, some key things that had to be done for me to even get close...
There are 2 sections in particular that I felt were crucial to good lap times:
For the snake section (in between checkpoints 1 & 2), keep the car in 3rd gear. This can be done by pressing the L2 button, preventing automatic transmissions from shifting up to 4th. Without doing so, the LS will likely shift into an under-powered gear (leading into a hill), averaging 76-79mph for the next 2 turns. Keeping it in 3rd makes it possible to hold this section with a 78-81mph average, finally releasing when the car straightens out (just before hitting the rumble strip leading into the 2nd checkpoint). Doing so has allowed for me to consistently break 34 seconds for T2, even with 1 red tire.
For the final chicane section (in between checkpoints 3 & FINISH), also keep the car in 3rd. If your goal is a short lap time, and not a perfectly-raced lap (like a time trial), you can skip through the dirt for the FIRST (not second) part of the chicane to get a better exit trajectory. Staying on the road, you can maintain 60, which is still good enough for good lap times. I think my best exit mph was 74, but keeping it above 68 will set you up nicely for the final curve. Keeping the car in 3rd gear, you can get trough the final turn as high as 80, releasing it when you finally straighten out for the finish line. Allowing the LS to shift into 4th will likely sacrifice speed, as it will tend to do so in the midle of the final turn.
You can win this race with an off-the-shelf LS no oil, no tires... just keep the car on the road for the most part, and try to run at least 6 laps before pitting. Averaging 1.45-1.47 for non-pit laps will keep you in good shape if you do.
I ended up racing this one about 7 times before I finally won the car I wanted (the F688/S) and saved. Funny to think I may have gotten it sooner without trying to press the button when the circle was lit under it. LOL :\
Better luck than mine,
Hazzard