Liu, I will try to take the EGR tube and other crap apart to clean off the carbon deposits. I too don't want to do the cash thingy each year.
If it gets slight warmer, I will do it, if not I have a patient of mine who use the service of a BG product. There is a guy you can call, he will come out and clean all those carbon for like 100 bucks using this great BG stuff.
google it and let me know. The mechanic will have do the same thing like me, take the EGR, tube BPT and clean it anyway.