My GF has a 2010 MBA 1.86 4GB. It became unusably slow and two different Mac specialists recommended a new logic board. I did a hardware test which turned up a code that seemed to relate to a thermal sensor.
After digging around on the web I came across this process (links don't seem to be allowed here):
"Fix MacBook Air kernel_task fix on Lion 10.7.3 (use these instructions as your own risk).
Before you do this, note that I recommend you max your fax using smcFanControl and if you've got an old system and if you are capable, open the bottom cover and clean the fan super-well using compressed air. I also run my MacBook Air on a Belkin USB-powered laptop lap desk with a built-in fan. You are about to unleash this CPU to its maximum, so keep everything as cool as you can or else you might burn up the CPU and/or mainboard.
I spent over 80 hours of my personal time figuring this out, so if my fix works for you, and if you feel like blessing me, send me a PayPal at chuck straughn at me dot com. No obligation, but anything you do helps me and my family. If these instructions are too technical for you, contact me and I'll do it for you for a small fee if you can afford that, otherwise I'm happy to help you for free and share the love.
1) Open System Information (under Apple icon in upper-left, click About This Mac, click More Info)
2) Click System Report button, under Hardware, find your "Model Identifier" -remember this for later use
3) Navigate to /System/Library/Extensions an right-click, Show Package Contents of IOPlatformPluginFamily.kext
4) Open Contents/PlugIns and Show Package Contents of ACPI_SMC_PlatformPlugin.kext
5) Open Contents/Resources
6) Find your MacBookAir?_?.plist (? = your model identifier from step 2) and delete the file
7) Reboot! Remember, anytime you do a System Update, you may need to repeat this process"
After following the steps described by above, written by "Chuck Straughn" the MBA is massively improved. It's still not perfect as it slows down after a while and needs a reboot, but it's definitely usable and has been for around a year. The process is simple to follow and easy to reverse, so might be worth a try for you. Obviously you do so at your own risk.
