hi,im having issues with my engine surging at idle up and down,from 1,000 rpm to 500 rpm,when i slow to a stop fast or turn the wheel it occasionally is stalling on me, i found a broken vacum line to the fuel pressure regulator repaired it,also replaced a cracked air breather hose to the valve cover,the electro hydraulic valve is defective and unplugged,coul this be the issue,what else can cause a surging idle and stalling issue,any help will be appreciated,thanks.marc