Ive got a 99 sable with the 3.0 OHV Vulcan with a bit of an issue. It started about a month ago and doesnt happen all the time. The RPM tends to drop to about 500 rpm or lower in drive at lights and sometimes bounce up then back down. Also, the tach jumps up at times and sticks for a second at times. A while back the check engine light came on and got the code pulled. It was the EGR valve. The light eventually went out but could it be that? The real odd thing is that when the rpms on the tach freak out the engine doesnt seem to change. It doesnt lope or stall or surge at all, it runs smooth as silk. Any ideas or input?