I don't know what
Join Date: Jan 2009
Location: United Kingdom
I had the exact same thing today. I live in England but am currently on a road trip around Europe with some friends in the Alfa 147 jtd 16v, was booting it for a few minutes at 120mph and noticed sparks coming out the exhaust, pulled over a bit after, and it was a really nice effect of sparklers on acceleration from the exhaust, i took a video too but wish now that it was a bit longer.
anyway, i turned off the engine and then back on, and the sparks lessened a lot, then hours later, the sparks finished, i assumed it was just the heat build up and either a build uo of debris is being exposed tot he heat and expelled... or the cat... but it seems fine now.