Hi there, im new to this forum and I just bought myself my first ever fiat.
Its a Fiat Stilo Multijet Sporting JTD 06 Plate.
I bought it the other day and on the way back the engine light came and the car lost power on the motor way, it wouldn't go above 60mph and to get there it would take a bit of time.
when i got home i phoned the dealer and he told me that this was common fault amongst fiats, that i was something to do with the lamber sensors, and that if i took it to a garage they would sort it for me, and he would pay for it.
So the next day i went to the garage and once they connected the computer to the car, the codes that were coming up where:

1. P0380 Preheating Unit Control
2. P0601 ECU Defect (EEPROM)
3. 01025 Undocumented Code
4. Boost Pressure Sensor Circuit

After they disconnected the computer, the engine was gone from the dashbord, so i made my way home since it was gone. when i was just about to park the car the light came on again, so off i was to the garage again.

This time when they connected the computer, the code that was coming back was
1. 01025 Undocumented Code

This time the engine light wouldnt go away. The garage guy said that he had no idea what it was, and that he couldnt do anything about within the next couple of days, which wasn't any good for me. So i phoned the dealer, and told me to bring the car back and his mechanic would fix it for me.
Now whenever i try to go over 90mph on the motor way, the car loses power and slowly goes back to 60mph or just over.

what i need to know is if this could be something serious, or is it something minor?
and how much would it cost to fix the thing?
and also why did those codes come up and then they were gone just like that?

thanks