I purchased a 98 QC 1500 4x4 318 recently and it idles nice and steady. When I'm cruising around and let off the gas to slow up for traffic and then get back in the throttle it kind of hesitates and shakes. Now if I get in the throttle form a stop or hard into it from any cruising speed it does not do it. Only when lightly getting back into the throttle after letting the rpm's drop. It does it worse the slower I'm going(due to trying to get the big sucker moving again). The previous owner said he had a miss awhile back and that he changed the plugs and wires and it fixed it. I don't know how true that is. He also had it sitting for awhile so the gas might be no good. So I filled up with premium today and threw in a can of injector cleaner. When I got home I put it in park and noticed that it does it when ever applying the gas in park. Any ideas guys?Thanks in advance for any help.