FWIW, when I installed my GD downpipes and testpipes, it made my car smoke a bit.
It is interesting though - I can't really remember the last time I heard anyone on the forum talk about this issue. I have personally seen this problem a number of times over a span of about 5 years in various vehicles but it just hasn't ever come into the spotlight on the forum (that I can remember specifically, but I know it has come up before). Have you tried searching for this topic?