Kevin, I'm about 2 hours north of you and I have storage insurance on mine so I can't meet you but if you need to you can bring your DME and we can drop it in my car. Sorry I can't do more for ya.

I think you could lower it a tad as long as it is warm (ala Jim / Draco's first post), and keep track of the turns.
Later, during a cold start, she should run abt 1200 until it warms up and the ICV does its thing to lower the rpm to idle. At that point you'll have a better idea if the ICV is acting up, or if you are starting to uncover some vacuum leaks. (But I think you'll be ok since it ran at 880)

Sometimes as they get old and develop vacuum leaks etc, and the idle drops, a PO may have attempted to raise the idle as a short term fix and thus masking a problem.

the thing with these cars is that you should NOT have to make any adjustments. if the idle is bad, something is making it bad. if the mixture is wrong, something is making it wrong. air leaks and a bad O2 sensor can do it.
same for the idle. a stuck or bad ICV can make it idle at the wrong RPM. the ICV should vibrate with the key on.

ok i lied, kind of. the throttle position swictch can get out of adjustment, especially if you mess with the throttle plate stop screw.

Did you verify that the idle micro switch is closed at idle?
If with the jumper it's at 880RPM then the base idle is set correctly. Then remove the jumper and the idle pops up to +1000RPMs something is wrong. But the engine MUST be fully warm to be at proper idle. While cold the DME will lift idle to 1100RPMs till the CHT sensor warms up. So I also suspect maybe an issue with the CHT sensor? And if the sensor is bad it can cause the rich running condition. You need to be sure that sensor is good. Here's a quick test for it:
1 - at 20C (room temp) it reads about 2500ohms
2 - engine fully warm it should read <100ohms
The sensor connector is the white one next to the speed and ref sensor connectors on that same bracket. Also be sure it's the 2 wire sensor the older 1 wire sensors should be replaced.

Thanks for the replies.

Dan: I don't think there are vacuum leaks as the idle changes when the oil cap is removed, but I will try the starter fluid sprayed around hoses to try to confirm. I know vacuum leaks can be tricky. Also, I don't think the PO made any adjustments since the original cap is still on the idle control screw and fuel mixture adjustment screw.

T77911S: ICV does vibrate with key on, also I looked into it while key on and noticed the inside sort of flicks back and forth while vibrating. Normal? Not sure about TPS but I haven't touched that.

Sal: CHT is new, old one was single wire. Tests ok at room temp. I have not verified idle micro switch operation, but I can hear it click when returning to idle position. How long do you think it takes engine to be warm just sitting in garage at idle?

I'll try the vacuum check and test micro switch and test new CHT at temp and report back.

Thanks again!
Kevin

Give engine 10 minutes to warm up at idle.

Bench test the ICV using this procedure I outlined a few years back:
http://forums.pelicanparts.com/porsche-911-technical-forum/360766-bench-testing-carrera-idle-control-valve.html

The ICV has 2 internal windings, 1 set is used to close the valve while the other set of windings opens it. If one set of windings burns out you will have a valve that goes fully open or fully closed depending on the set that burns out. It's worth verifying the valve with a simple 9volt battery.

Update: I took the car out for a drive and MAN! what a great car :) It ran great, pulled hard and sounded awesome. I think all the items I replaced trying to fix the studdering and hesitation were worth it. I can't say which item was the culprit or if it was a combination of a few. And I figure all the items were maintenance/repair items anyway. I still have the high idle, but I suspect a vacuum leak somewhere.

Can the oil cap test work but still have a vacuum leak somewhere?

To sum up, items replaced:
-spark plugs (old ones had a gap of 1.4!)
-distributor cap and rotor (old one was pretty bad)
-CHT sensor
-speed sensor
-reference sensor (all three of these were original and crumbling)
-O2 sensor
-fuel filter (original in car)
-DME relay (still have original as back up in case it was still ok)
-oil change
-tranny fluid change (I think the fill plug was last installed by Hogan)
-air filter (that last clip was a *****, especially with a failing engine pad)
-cleaned/tested ICV

I plan to run this old gas out of it (still at half tank) and run some Techron with next fill up.
Thanks for everyone's help and I'll keep you updated on vacuum leak search.
And for the fun stuff, my wife gave me a Momo prototipo for Xmas and I picked up a fabspeed cat bypass pipe for a great deal, so I still have stuff to do ;)

My guess is the plug gap was the most likely issue.
I suggest you get the base mixture tested and adjusted if need be, you need a WideBandO2 or a CO meter to do this. If you use a WBO2 I'd set the mixture at 14.2AFR just a tad rich.
I really do think you need to figure out why the idle is NOT at 880RPMs.

Sal, I agree this is not a case closed situation and plan to pursue the reason for the high idle. Thanks for all the help so far. The search for vacuum leaks will be this weekend hopefully and then on to mixture testing.

Normally if you remove the oil cap at idle you should notice a significant change in idle. If the idle does not change you most likely have a air leak. But the very best way is with a WBO2 and looking at the AFR reading, a decent air leak results in AFRs >16.0 you really need to know what the base mixture is at. That's the best next step.

Not to bring back an old post, but I wanted to let you guys know I found the problem. The alternator. It never occurred to me that the voltage might be low because the car always started and ran, but it was also always on a battery tender. So it never presented as a dead or low battery or weak charging system. I changed the alternator and she fired right up and settled in at a nice idle. Now I can concentrate on more fun things to do (might get a steve wong chip). Thanks for all the help!