loot87, your symptoms sound familiar. Check out this thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/275616-cis-hard-cold-start-if-youve-ever-had-problem-please-read.html

All AARs are not created equally. Some remain partially open when warm resulting in mixture and idle tuning done to compensate for the continuous vacuum leak. I have removed the AAV and the AAR on my engine and have tuned appropriately for it.

You can easily determine if you have a check valve or fuel accumulator problem. Unplug the electrical connections to your WUR and AAR. Turn on your fuel pumps for 1 minute to fully pressurize the system. Hit the key. If the car starts as it should you have a leak down issue.

i had the same symptoms. sitting for a spell after driving, it would be a beotch to start. i checked my CIS pressure and i found my at rest pressure going down fast. one of the test is to find the source of the leakdown. the first move is to build the pressure up again, and shut the car off. when the pressure takes a dive, you shut off the valve on the pressure tester. if the pressure holds steady, then it is leaking down thru the WUR. which was my case. new WUR and all my issues went away. the key is to test the pressures.

My pressures are dropping pretty quicky after about 10 minutes. The line to the WUR is closed. I replaced the check valve and nothing changed. So what's next, the accumulator?

What is your system pressure?
What is your pressure after 10 minutes?
What is your pressure after 12 hours?
What line is closed off on the WUR?

System pressure is 7.
Control pressure is 4.5 with 85 degrees ambient.
Pressure after 9 minutes was 1.4.
Pressure after 10 minutes was 0.
The tester line to WUR is closed so I am just reading the pressure from the dist.

I had a condition just like that, in fact it leaked a bit quicker. It turned out to be a leaking fuel injector that was draining into the cylinder.

You can actually test pretty easy for this by getting a few small jars and just letting the injectors sit in them after the pressure test.

Pressure after 10 minutes was 0.

Looks like we know what the problem is. The engine will flood if you have injectors leaking down. If that is not the case I'd look at the accumulator next. There is a diaphragm at the bottom that can rupture resulting in loss of system pressure. Does your accumulator have 2 outlets on one end and 1 on the other? If so you can pull the bottom return line. If memory serves fuel will spill out if the diaphragm has ruptured. A schematic of that unit should show this. I can't look now but will try to find one a little later.

Thanks for your help Rarly. When the engine is warm, it just turns over for about 30 seconds to a minute before it fires. How can I tell if it's flooded?
I'll take a look at the accum and see if it exhibits the behavior you are talking about.

Thanks Scott. I'll also test the injectors.

If it takes approx. 30 sec. for the engine to start, it usually points the fuel accumulator or the check valve located on the front fuel pump. It takes a while to pressurize the system when it is fully discharged. Also check for any leaks in the line that could cause the system to lose pressure. It doesn't take much.
If your exhaust is really sooty after turning over for 30 secs and then starting, it's not a loss of pressure that is causing your problem.

I replaced the accumulator over the weekend and now the residual system pressure stays at 2 bars for 30 minutes. Cold start is much stronger than before but it just started snowing here, so I'll have to wait a day to check the warm-start to see if I fixed it. I think I did.
Thanks to all for the help. I wish I had resources like this 15 years ago when I was trying to fix my 68 Mercedes 200D (blown head gasket after 400k miles).