Hey everyone. In last 12 months I have done the following to my 1990 5.7 Silverado 1500 (170k miles)...replaced fuel filter, distributor cap/rotor, plugs/wires. Just recently engine developed a "miss" between 35-45 mph. I checked to make sure a plug wire had not come loose or a cracked vacuum line. All seemed ok so I had repair shop look and they could not find anything and suggested I drive on until it got more obvious. A week later it gradually got worse so I took it back. They replaced spark plugs (they did look like they needed it but had only been replaced 12 months ago). Mechanic said skip was better but it idled a little high but would lower after driving it. I cranked truck to leave and it was idling about 1500rpm. I literally had to keep my foot on brake to keep from taking off like I had foot on gas. I took truck back and they are looking at it again today. It actually idled ok before plugs were replaced. I suspected a vacuum line had gotten knocked off but I did not see any problem. Any idea what happened? Check engine light is not on and I using paper clip method it is not showing any codes. I am at a loss and any ideas would be appreciated.