Ironically, the 40-50 degree difference in ITT turned up after the HSI, so yes from one day to the other. Now, we had the gearbox and oil cooler exchanged at our right jet engine (CJ1+) 3 days ago, which has nothing to do with the bleed air system/ducts. Nevertheless, now, at the first flight after the maintenance, the ITT in the right engine is about 15 degrees higher than in the left one so I´m wondering if taking apart half of the engine and re-assembling it with the two new parts did have some effect on that (never observed that phenomenon before).