I just recently purchased an 07 a4 with its original warranty still intact and I need to know if i got my car chipped if the dealership would be able to tell if hypothetically i had to get anything fixed. Are there certain diagnostics they can run to tell if a vehicle's ECU has been modded? Or if I set it back to normal before I brought it in would they even be able to tell

 

I think if you set it back to stock they're not supposed to be able to tell.

 

With APR you can toggle back to stock mode. They also have a security code lockout feature that you can have put on. Only then could they switch it to Performance mode and tell. APR is on sale right now with a ton of free features that normally cost extra.