I was messing around today on the way home from work with a 335. We did a couple of spirited pulls and I experienced some knock. After a fun run I let off the gas because of some cars I began to approach. I down shifted a tad to early into 4th but luckily it wasn't enough to bring the car to redline but I did reach about 5500 rpm. I looked in the rear view mirror to be aware of the 335that was behind me. I noticed sparks in my rear view mirror, it seemed to becoming from my exhaust possibly. They seemed to be rising up the back of the car probably due to the air being updrafted from underneath the car. What could have possibly caused this? Car seems to run fine and sounds completely normal. Any opinions? Gonna pull the plugs and do a boost leak test as well. I mine as well check the turbo to make sure all is well while I have the intake pipe off.

 

Dislodged carbon deposits burning from your pull? I don't think I've ever heard of this...

Does your car have a cat? If so crap coming out your exhaust is even weirder unless it was the honeycomb in the cat somehow coming apart and flying out your exhaust...

 

No cat, I checked the turbo but no issues, I will post pics of the spark plugs...