Seems like you guys are new in modding.
In general, when you mod your car, warranty is voided.
Others offer engine warranty by wording it differently to make you believe that your existing BMW warranty is still in-tact.
You need to read the details too.
It is also void your warranty, it just being replaced by their warranty.
Few horror stories about them, they will put you in the middle of the fight on whom going to pay the bill.
I just heard another one last week from my local customer.
While in this case, the last statement is for legal purpose since the CARB certification are still pending and it is a generic aftermarket performance label that many many manufacturers put out to protect themselves against the government.