Anyone have any more ideas or RESULTS with the aformentioned?
Yes!!!
Like I said months ago, window cleaner and fine grade steel wool!
I'm not making it up, I know it works and have cleaned literally hundreds of tailpipes this way.
If the buildup is minimal, you could probably use some kind of metal polish like a few people mentioned. But if its something that has been accumulating for awhile just go to Home Depot, buy some 000 grade steel wool, spritz your tailpipes with windex and slowly work away the build-up.
If you don't have time to run to the hardware store, I'm sure you have some other mildly abrasive substance around the house that you can use to agitate the stain....like the pot-scrubbing side of a kitchen sponge , the scrub side of a mop head (might be a little akward) or an old toothbrush maybe? The steel wool would be faster, but I'm sure you could find a suitable alternative in a pinch.
If you are concerned about steel wool being too harsh, that is why I recommended a fine grade that, when used with a liquid cleaner like windex, will not damage the metal finish.