EGR valve 1980 GMC

[marvxyz1]

I've got a 1980 GMC with a 6 cylinder engine. Run like crap for a long time --New plugs rotor coil plug wires. Still runs like crap. Also has a flutter, when you pull out from stop position. I disconnected EGR valve and plugged the vacuum line going to it . Truck runs like a champ now. The EGR valve is relatively new(not many miles on it. I think it's carboned up). Question is: How can the carbon be cleaned from the motor and EGR. How long will this cleanup be good for??? By the what does lol mean??