07-10 HONDA TRX420R4X4: Big Gun TFI Power Box The technology behind the Big Gun TFI Power Box is that it functions like a carburetor. It takes the knowledge and experience that many riders have and converts it to a fuel injection interface. The TFI interface makes it easy to tune for different modifications. The TFI Power Box is to be used on EFI ATVs, UTVs and dirt bikes that have performance enhancements which require more fuel to run correctly; such as pipes, heads and even big bore kits. With its patented technology, this box does not default computers or trip engine lights.