OP...thank you for putting together this great DIY. I followed most of the instructions (minus the powercoated tips) and the results are unbelievable. While I had the Supersprint mufflers on the car, I took advantage of the situation and painted the OE mufflers. I used matte black instead of semi-gloss because I wanted to hide these "sacks" as much as possible. I had initially planned to use engine paint, which is a higher temperature paint, but found out that those required priming. Didn't want to go the extra steps required to prime it, I went with the matte "grills" high heat paint instead.
The end result is night and day. You don't even noticed the "sacks" anymore when standing behind it. Now...just wondering how durable this paint would hold up
