The Beast is alive!

I finally fired the 65 fastback I've been working on. It is a 289 w/aluminum heads, headers, MSD ignition, and two 500cfm Weber/Edelbrock carbs. My issue is this:

She has a warm idle that is way too high(I have a tach issue that does not allow me to know the exact RPM)
The idle screws are backed off to the point of no longer touching the linkage. The cam is .512 lift  with .060 longer than stock pushrods and 1:6 ratio roller rockers. The base timing is at 15 degrees. It needs more advance, but it helps with idle speed. I think I need to fatten up the idle mixture. It acts like it is idling lean. Any ideas? This is my first multiple carb engine. Thanks!  
1967 Fairlane 289-4v auto...for now
2007 Mustang
1997 HD F-250
2006 Taurus

Sounds like you could possibly be chasing an air leak.  Also make sure that the fast idle cams on the carb(s) is not hanging.  For a start, I'd look to have the primary throttle blades open just enough to see maybe .010~.020 of the transfer slot and the secondary blades (and the air vane) closed.  15 lead should be a good spot, not sure why you'd think it needs more.  A generic curve might be from 12~14 to around 34~38 or so.  Dual carbs is not going to be too much different (IMHO lol) than a 4 corner idle Holley.  Start with the idle mix screws out about 1 turn on both, then you just have to put a vacuum gauge on it and tweak it from there.  
1967 Falcon 4 door 351C-4V
1970 Mustang 351C-2V
http://raceabilene.com/kelly/hotrod
Owner built, owner abused.

I will look at the fast idle cams again this weekend. I first had the timing at 25 and the engine was more responsive and had a "smoother" sound. I did check the idle screws before installing the carbs. Both were 2.5 turns out from the factory-and they are still at that setting. I have yet to put a vacuum gauge on it. I will do that, along with installing a new tach, this weekend. Thanks.  
1967 Fairlane 289-4v auto...for now
2007 Mustang
1997 HD F-250
2006 Taurus