Stains on exhaust tips
 

So hey guys. I am not new to car detailing at all, and my Zs have won my local CCA Concours a few times, but I have a problem I can't seem to rectify.

My exhaust tips on my 4.4i Sport (the black chrome ones) have some burnt on stains. I have cleaned and tried polishing them with Eagle One metal polish and a bit of Blue Magic on a mf cloth without success. What do you guys recommend? I am hesitant to scour them with anything too abrasive as I am not sure how the finish will react.

If I can't clean them, will 4.6/4.8is chrome tips fit as a replacement?

Same with my sport tips..So hard to clean off the burnt crud lol. for the 4.4 mufflers, you'll need to have the black chrome tips removed and have a muffler shop weld the 4.6 tips on exaust pipes.

sorry guys I never worked with the black tips on these cars.