Hi. I'm Phil from Cleveland, OH. I have a '94 Chevy G20 van with a 350 engine. It was recently tuned up with genuine GM parts (distributor cap, rotor, wires, and plugs. After it warms up, it idles rough and almost stalls out, like it's running too rich and "loading up". Also when accelerating at 50 mph on an upgrade (trans in overdrive) it occasionally misses or "jerks". The jerking goes away if I drop down into regular drive position. Any ideas?