1994 GMC Jimmy EGR Valve

I have a 1994 GMC Jimmy. We got it about 10 to 12 months ago and ran great for about 3 to 4 months. Then it started sputtering and acting like it wanted to cut out and the check engine light came on. After haveing it check we were told it needed a new EGR valve. We did get it replaced for $360. We thought it was done and over with. Well about a month later it started doing the same thing. I took it to an other machanic because I thought this one riped my husband and I off. Well they said that there is carbon build up in it and there is no way to get rid of it from your engine on a truck as old as mine. Now I spoke with the person we bought the truck from and he said that when he has had carbon build up he would spray water from a spray bottle in to the breather after the engine is warmed. While the wather is being squirted in to the breather to keep the engine on a low rev. The enging would then start to sputter some and after a little bit more it would start running back to normal and then you can stop praying the water. He said he has done this to he motercycles and a few other cars. I am wondering if that could really help clean the carbon out with out damageing anthing? If not what would be an inexpencive way to clean the carbon out of my enging