Most race cars and racers dont care very much about idle; an old trick was to set idles deliberately high so when the brain tells you to get off the throttle the machine actially carries more speed.

Your car is a 87 where you cannot adjust the idle and it should be 675 rpm.

 

Now, no-one knows now how cool your car really is.......

Back "in the day" god, I'm dating myself here......we had a 396 with a just stupid cam in it, and and idle under 900 was just not going to happen.......

But, damn it sounded cool! And once you got some revs happening........

But, we didn't have to worry about "clean air" testing and back then we could still drop into the local airport for a Friday night load of 100/120 avgas.....

 

Rob,
The carbs are horrible as were the intakes for getting proper fuel into the cylinders.
My idle wasn't the best until I found a setting on the sharktuner allowing the brain to know how control the 60# injectors I'm running.

 

LOL!
And we had a Holley 850 double pumper on that thing, Edelbrock Tarantuala manifold...yada yada yada.......ah, the memories.....

60# ?

 

Rob,

Yes 60#, if you didn't know the injector size, you wouldn't know it had them either.
Idles like stock, just a little higher.......

 

most stock S4's and most 928's in general tend to idle very smoothly........high idle, hunting idle are easy symptoms something is wrong.... My Estate is bone stock internally....it fires and idles perfect.....no matter how hot or cold....once the fuel pressure hits, it starts....

 

I've so got to get out to BC......