idles rough

My 94 blazer is idling strange, I changed the cpi about a month ago, and unclogged the EGR Valve. It has been great until 2 days ago. It has started to idle rough, sounds like i am tapping the gas pedal every few seconds, the faster I go, the less it happens, and the smoother the ride. It shakes when I turn it off. And the service engine light comes on and off. I do not smell gas, and there is no gas in the oil (like there was before I changed the CPI), and I checked under the plenum(?) where you see if one side is washed, but neither were. When I checked before having the CPI fixed, one side was definately washed. Do you think this sounds like an EGR problem? Is it common for them to get clogged this often? (Maybe all the gas rich oil gas running through my engine?- we have changed the oil a few times, trying to clear all the gas out, and I think it is finally clean) Any advice would be greatly appreciated!!!