Alright, I finally got my MacBook Air 1,8 back. After I took it to the store here where I bought it (Media Markt) my Mac was gone for over three weeks. After many discussions I finally knew what happened to my Mac and what happened was nothing. The technician said there was no fault and the machine would just run fine(!). Of course I didn't agree since obviously there is a fault since I already have my 1,6 MacBook Air back after repair and it works beautiful.
So I took my Air to a different Apple retailer who was fixing my other Air before. And after I explained to the technician the problem he swapped the logic board and the fan and guess what? Now the Air runs how it was supposed to in the first place.
I just had Skype Videochat on running, Flash CS3, Dreamweaver CS3, Illustrator CS3, Photoshop CS3 and Safari all running and switching back and forth working while talking on Sykpe.
*NOT A SINGLE CORE SHUTDOWN* happened while I was doing this for a whole hour and the Mac didn't freeze on me either.
Before I handed my Mac in to get fixed I did the same thing having ONLY Skype running and my whole Mac froze after it becoming too hot.
Like I originally thought. Apple didn't construct the MacBook Air the wrong way. Personally I believe it is the thermal paste and that the technician here is just more skilled then the one's who are working in the Apple factory. All I can say is my two Airs run now perfectly and they are able to cool themselves down without overheating.
If you are having the same problems that I had insist on a fix, a hardware fix. Don't settle with a wrong pieced together Mac. It is worth the trouble having it fixed trust me. I'm happy with my Air now 🙂