Will it really add 35 hp?

That is the seller's upper claim. Real gains from a plug-in module are usually smaller and vary by engine and model year. A dyno run before and after is the only way to know for your car.

Does it fit my 7-Series?

The maker says it works with any transmission, turbo, supercharger, intake, exhaust and diesel setup. Confirm the connector and model year with the seller before ordering, since 7-Series engines changed across generations.

Will it void my warranty?

A piggyback module that alters engine signals can be flagged by a dealer, and BMW may deny powertrain claims tied to it. Removing it before service helps, but stored fault codes can remain.

Can I install it myself?

Yes. It plugs into the engine computer connector with no cutting or splicing, and the maker quotes about two minutes. Basic comfort with the engine bay is enough.

Will it improve fuel economy?

The maker claims up to 6 mpg. Real-world savings depend on driving style and are usually modest; a chip that adds power often costs economy when you use it.