Mine look like tarnished silver on the inside. What do you guys use to keep them clean?

 

I don't bother cleaning the inside because they just get soot from the exhaust on them. For cleaning the outside though, I just use soap and water then hit them with some Mother's polish when they need it.

 

Wenol polish (blue tube)

 

you can use steel wool on the tips to get the varnis off too, it you have true stainless steel tips it wont affect its shine

 

SOS pads to clean SS tips and a little wax to seal them up. Test a spot first if you are worried about getting scratches that you will then have to buff out later. This worked fine on my Magnaflow tips and they seemed to get really dirty during the winter.