need some input. 1994 Yukon SLE, 5.7, 4x4 stumbles at 1000 rpm but pulls herself together at 12-1300 and runs good. How can someone check an EGR valve w/o a vacuum tester? Took off lines at EGR valve and plugged both ends, truck runs fine, put the lines back on and the stumble returns. Lines look good ( no cracks or damage but one rubber end is a bit loose ). Bought the truck a lil over a month ago, guy who had it before did some monkeying around under the hood and now we have to figure it out. Have the issue tracked down to possibly 3 things, EGR valve or solinoid, ECM or worn/stretched timing chain so I'm tryin the cheapest first
