F1Brits_90 - There are so many inconsistencies in the rules.... If you run an illegal part in qualifying, you are sent to the back of the grid (but still have the chance of winning points). The principles of parc-ferme are that if you run an illegal part in qualifying, you should be forced to run the same spec part in the race - yet if the illegal part was found after the race, you'd face exclusion from the race (and lose all points).
The nearest to your example was BAR in 2004/5. Effectively, the team had run with an underweight car for the entirety of the 2004 season, but it was only in 2005 when this was proven. As such, they were banned for 2 races in 2005 (and no retrospective action was taken).