long story short. this isnt my car. its a friends. he bought it as is with no idea of what cam is in it. all i know about it is that its a stock head ls1. has a twin filter cold air intake. i have foold with this thing for hours and can not nail down the idle. on cold startup it flares to about 2500rpm. then when it idles down it just runs rough. any help would be greatly appeciated.

98 corvette.
ls1
stock heads
unknown cam
cold air intake
looks like stock injectors
fast 90 intake.
longtubes
corsa exhaust.