EGR Valve
 

What causes this to go? I recentlly had to replace mine because my mechanic said he could not just clean it. It had to be ordered in and all.

Anyone know what caused this and how to avoid future problems?

Carbon build-up in the valve assembly. Exhaust gas flows through this little pintle valve and as it becomes more and more clogged up it works less and less. Sometimes they can be cleaned, sometimes not.