You can ask the SM about mods you have in mind. Be aware what he says means nothing. Rather it is what the factory spells out in the warranty booklet what is covered what is not covered.
I do not have a warranty booklet with my M2. Just searched and found a PDF online.
Here is the link I used:
https://www.bmwusa.com/explore/bmw-v...nty-books.html
A paste from the document:
WHAT IS NOT COVERED
The car or any part of the car, unless the failure causes the car to fail to conform to the applicable emission regulations.
Malfunctions, including consequential, caused by negligence, misuse/improper operation of the vehicle, environmental influ- ences, flood, accident or fire damage.
Malfunctions, including consequential, caused by improper adjustment/repair, modification, alteration, tampering, discon- nection, improper or inadequate maintenance except if one or more of these occurred as a result of repair work that was performed by an authorized BMW center under warranty.
For gasoline engines malfunctions caused by the use of leaded fuel or fuels containing more than 25% ethanol, or other oxygenates with more than 2.8% oxygen by weight (i.e., more than 15% MTBE or more than 3% methanol plus an equivalent amount of co-solvent and/or as specified in the Owner’s Manual).
Spark plugs, filters, and similar maintenance items are not covered under this warranty at or beyond the first replacement interval, or if the part has been replaced earlier for reasons other than it being defective.
Any car on which the odometer has been replaced or altered and the true mileage cannot be determined.
Any car on which the Vehicle Identification Number (VIN) is altered and/or cannot be determined.