I did the search an found either a vacuum leak or some relief valve. I checked the vacuum hoses around that area an took the top of the intake off. I also did the carb cleaner spray down an had no change in idle. I even got the stethoscope out an couldn't find it. Seems to be coming from around the EGR in that area. Sometimes it only does it an idle an sometimes it only does it at a certain rpm like 2000. I'm baffled. Next step is to take the whole intake off. Where's this relief valve. Oh it's a 94 Sts NS.