Originally posted by Terry Haines:
Cat meltdown.......
what about if the some of the passages in the cat are clogged with carbon or other deposit. Under high power operation when the EGT and flow rate are highest the catalyst gets hot enough and back pressure high enough to dislodge these small pieces that have become incandescent due to the extreme heat. They then are expelled out the tail pipe and look like sparks since they are glowing.
