I have a 2000 VDP and the chrome tips have collected a bit of tarnish over the years, mostly from the lack of maintenance from the previous owner. I searched around the net about cleaning the chrome and didn't get any for exhaust tips but found a good one on bicycle fenders. I tried it and it didn't work too bad, I think a bit more elbow grease will garner better results, but I wanted to share the immediate ones. Mind you this took about 30-40 minutes and multiple uses of the foil since it crumples tightly somewhat quickly and you have to make another.

The first 2 are of the untouched drivers side one. The next is a comparison of undone vs done (notice the multiple foil ***** on the right). The generic foil and approximate size used. Then you ball up the foil as such....dip it in a cup of water...apply elbow grease like your using a scouring pad until the foil is collapsed hard, clean off with a towel (you can see how dirty mine got)...repeat making another ball and using elbow grease as many times as needed and then 'whalla' the results. No the tips aren't perfect (after all they are 15 yrs old), but they are a dang sight better than before.
I did seem to find a bit of a quicker effect using warm to hot water. I put in some borax at the end to test that and I saw no improvement using it, so I would skip that. I must add, I didn't think the foil would hold that much water, so be advised, it will get a little messy.

 

I use some bug and tar liquid ..and then a light metal cleaner. If they really needed a polish Simichrome would be my go to product.

 

I find getting the heated on exhaust residue off the issue with those products. They work great on the rest of it and probably would be a good finisher afterward. I may even try that later to see and update.

 

It's an interesting use of the AL