Well, without hearing the engine noise my best guess would be the alternator possibly. When the alternator loads and unloads you can not only hear a change in the engine RPM but you can actually hear the alternator as well. Depending upon the load placed upon it and the current state of charge in the battery the results will vary anywhere from barely noticeable to you can't help but notice it. Again remember, this is just a swag as I can't hear your car over the computer. :)

The ignition contact plate is not too bad at all. Remove the instrument cluster, should be a screw in each of the lower corners under the little plastic covers. Remove the harness connections from the back of the cluster and set the cluster aside. There should be enough extra harness that you can pull the cluster out and roll it up ontop of the dash so it sets there upside down while you pull the connections off. Now look in the hole where the cluster is and you should be able to plainly see your ignition contact plate. It sits on the right side of the steering column and has a round push on electrical connection on the end of it with about a dozen or so pins on it. Remember your key turns this thing so it has to be right inline with the key and where you put it in at. Order up a new one and you will have it in your hand so you can recognize it as soon as you see it. The only real pain in the ass is the fact that they used slot head screws (2 of them) to hold it in. No problems coming out, but getting the screws to start can be kind of fun. When you put the new plate in place make sure that the little piece that indexes it is in the right position, if it is not you can put a small blade screwdriver in there and twist it to the correct position. If you cannot reach the lower screw from the top go ahead and pull the kick panel out of the way, the one that is above the driver's knees.

Mark