I picked up a brand new MK8 Fiesta ST in november, drove for a few hundred miles and everything was fine. I then decided to fit an induction kit (Airtec). Whilst removing the original airbox, i was a little heavy handed and managed to crack the cold air pipe. After driving for a while with the induction kit, i started to get a check engine light so decided to put the original airbox back on the car. After this the car started making a high pitched whistling noise on acceleration. You can't really hear it at idle, or when pulling away in first (not sure if this is just the normal engine noise drowning it out) but it becomes really apparent at around 2/3k revs in second and beyond. Car is performing exactly as it should, doesn't feel down on power.
Took the car into Fords who said it sounded like it was damage to the turbo and that the turbo would need be replaced at my expense, since i'd potentially caused damage. They advised (off the record) to take it to somewhere else to have this done where it would be cheaper. Car then went into a turbo specialist who had a brief look/drive in the car and said that it does not sound like it's coming from the turbo and that it sounds like it's just air coming through the crack in the pipe. I'd already got a new airbox on order so got this fitted to the car with no improvement. Spoke to turbo specialist again who said that they still don't think that it's the turbo but quoted me for a replacement anyway (ended up more than ford) and said it could be something rattling, or a gasket or the BOV and that i should go back to fords which made sense to me since if they find the problem and it turns out completed unrelated to what i'd done, then it would be covered under warranty. So i took it back to fords and they took it out again, still thought it was the turbo and that they are happy to get the turbo out and examine it, then replace if needed but said it would be cheaper elsewhere again. Took it to another well regarded local garage to get a third opinion and they said that they don't think it's an issue with the turbo, that it could be an air leak and that they can check all pipes and do a smoke test to see if they can find anything. This came up with nothing, they said everything was fine.
Not really sure where to go from here. No one seems to know what do to next apart from ford who want to take the turbo out, but with the specialist saying that it's not the turbo i'm thinking that this will just end up being a waste of time/money. The only real explanation for what i did causing a turbo issue surely is a bit of plastic making it's way up into the turbo, but this seems very very unlikely. Perhaps there is someone else out there having a similar issue?
Any advice is appreciated