Maybe both of you played with the coding?
If you get a diablo and don't change a thing it's 621 hp with only na tunes availible.
If I was you and wanted to find out how to set it up, first ask a mod to move this to the settings forum.
However, I can give a run at your question now and tell you the most important factor... course.
What course do you want to run?
If your looking for a "one-size-fits-all" setup, then I would go with even everything.
Even and in the middle of the slider. Then learn what each item does, then play with them in each direction...
Oh shoot.
I know... go to the olr forum and look at booms new tuning guide.
It has over/understeer and every other concept.
Once you learn those, you will more than likely be able to setup your own car and base changes on each course as well as what you learn from other peoples setups.
Oh yeah, thats another thing... please post your settings that are currently used, as well as the accurate stats for the cars hp. (if it really is 60,000 or even 6000... then I have no clue what to say)
Later, and good luck