Here's what Dinan says about warranty on their website.
Product support is another important aspect of the Dinan philosophy since we insist on equaling the after-sale service and support that BMW owners expect.
With that in mind, we offer the best warranty available anywhere.
Dinan's warranty matches whatever period remains on the individual New Vehicle Limited Warranty for up to 4 years or 50,000 miles. Exceptions are turbocharged, supercharged or stroker engines for which a Dinan Drivetrain Warranty is available.
Our current 2 year/unlimited mileage warranty applies to products installed on those vehicles no longer covered by the manufacturer's New Vehicle Limited Warranty.
And the installation of Dinan products will not affect your new car warranty coverage. So you are covered mile to mile, year to year and bumper to bumper