Today I was bored and I decided to record my cars exhaust with my phone. The car was at about 200 degrees when I did it. I held it close to the tail pipe and I felt something hitting my hand. When I pulled my hand away and looked at it it and my phone were COVERED in black dust (carbon maybe?). The car is all stock with a flow catback hi flo cat. And if it matters it smokes on startup valve seals. What could it be?

 

ever heard of the phrase "blowing the carbon out"?

 

Lol, its probably blowing buildup out thats in the catback and muffler, etc. If it's that bad, you might think about a tuneup. Long-term carbon buildup in the exhaust could be from a rich condition, say from poor tuneup condition, a bad O2 sensor, etc. O2 is a typical culprit because as they fail, they tend to fail "safe", meaning they fail reading lean, causing the computer to add more fuel. They continue to do so, more and more drastically, causing the computer to adjust the trim tables to compensate for a "lean" condition that doesnt actually exist. Make sure a good tuneup is done, replace your O2 sensor if that is in question, and reset the computer to make sure the trim tables are zeroed back out.