I'm having the same problem. A mech buddy said that it's related to carbon build up. The mentioned a product called BGZ 109 should help this. If it don't it's a expensive fix! Talking about taking apart the upper half a letting parts soak. Hope the BGZ 109 stuff works! Can't afford the fix it bill that will come w/ this. I'll keep ya posted on what happens w/ the BGZ 109. Once I get this stuff cleaned up I'm planing to do the EGR delete.