I think we're about to find out how well hydrocarbons work in 134a systems, and not just from you. Still, don't mix the gasses and be sure of the oil miscibility. Your car came with PAG oil.

If you use hydrocarbons, do not "release" some of the vacuum before charging. You don't "release" a vacuum. Instead, the act is letting air in. Air contains moisture, and moisture will polymerize with the oil.

I did pull vacuum on the system. 10 in hg, as was specified on the duracool website. (I did this with a hand pump meant for brake bleeding and vac testing. Can you tell I want cold air in my car???????) Then I added 3 of the small cans through the low pressure port. After running the system on LO while stationary, it went right down to 48F according to the cabin temp air sensors. After the car sat like that idling for 20 min, the temp was 52F. ( was filling a sprayer during that time). Then I took the car out on the highway, and at 70 mph, the core's temps were registering 39-40F. Now, we'll see how long the system works like that.
FYI, the pressure of the refrigerant was just over 60 psi, while the guage empty was 15. Seems the pressure requirements are much less with this product to get the same temp drop.....
Will keep updated....

A/C Problem
 

Blue is low side, Red is Hi side, yellow is for filling bottle or vaccuum pump. Also you might want to check this site out it has a great setup to help you troubleshoot your problem. http://www.eclassbenz.com/node/27 Hope it helps.

10" is not much of a vacuum, and not enough to boil any water out at all. I really don't think much of their instructions to add air to the system. And not pulling a real vacuum is the SAME THING as adding air!

I guess we'll see what happens.....

So, now continues the saga of the heat. As it can get cold here at night (6C the other night), I want my heat working.
So, I ran the following tests. I pulled the plug off the duovalve. The three wire plug. I then started the car and turned the heat to min. I then took an electrical tester, and put the ground in the center and checked the outside connectors. It was reading just about 12 volts. I then checked the resistance on the duovalve. It was somewhere around .015 ohms for both sides. Next, I checked the pump at both sides of the connector. Read about 13v. so, I shut the car off, and got a 12v battery, and some jumpers. The motor ran when I hooked it up, and both sides seemed to click when I connected the jumpers to them. It was hard to hear, but that seemed to be a case. I'm starting to think that it's just a bad rubber inside.
A few weeks ago, I picked a spare up at a scrapyard for $175. I ran all the same tests. The click for both sides was audible, and the motor ran properly. So, I closed random valves and blew through them (I don't like the taste of antifreeze), and some seemed the close when power was applied to them. Both sides seemed to operate properly. I guess I'll just pull the old one out, and put the other one in. I'll take the one that in my car now apart and see if I can find a way to repair the rubber inside....

I installed the new to me duovalve tonight. Seems to work just fine. Temps on both sides were about 77-78C according to the sensors.
Will keep updated.

Junkyard duovalve still working. Not hot enough out to see if the AC is still working. I had to charge last summer, and overcharged a bit.
I evacuated here a few weeks ago, and put in a weighted charge to keep the defrost working properly...
MattL, The 10" that was recommended was for a system that was still sealed, and you were just sucking out the old refrigerant. They recommend 29" if a system has been opened.
Before anyone says anything about using r134a, it's almost impossible for a diy guy to get it. You can only buy 50 pound bottles, and I heard it's a 4 month course to get certified to buy the stuff. Shop wanted $300 just to do a charge, and that didn't include any leak detection. Leak detection would have cost in the down payment on a new S classe territory.
The government in Canada where I live is phasing out R134a. R12 is beyond impossible to get, and trying to bring a can across the boarder is jail time. Trying to bring across the small cans of R134a without certification can net more time in the clink than arms smuggling from what a customs officer I asked told me.
I get very uncomfortable at temps above 22C and even in temps above 28-32C depending on humidity. My body isn't conditioned to deal with heat. I deal much better with temps around freezing. So, no ac isn't really an option.... For those of you in the south, that would be like telling you to go without a heater around 3C. I'm perfectly fine with that with just a long sleeved shirt or light jacket. Most of the people from the deep southern US would show signs of hypothermia...
As for the fire hazard, it's there. It's the position we're in...
There are no special fittings required by Canadian law. Just must be labeled. Which is done. It's not illegal in any Canadian province to use a hydrocarbon as a refrigerant.
Rather than arguing about what should and shouldn't be used, I"m just playing the hand I've been dealt to the best of my abilities.