There are no aftermarket Ridgeline performance chips, the 3.5 L is at the limit of the transmission.
There are a couple of folks that added an aftermarket turbocharger (that requires a lot of custom pieces to fit in the engine compartment). I doubt that it give much performance as the computer is not tuned to handle the extra air.
There is a 'block' from Crawford Performance that raises the position of the sensor installed in the air cleaner housing ( does not apply to pre-2009 models).
The claim is the sensor mod will provide better mpg (up to 1mpg). A few have tried it and have found some improvement.
There are no claims for any noticeable increase in power.
Jumping from regular (87 octane) fuel to premium (91 and above) will give up to 10 hp at the top RPM range. This is in the owner's manual and is recommended for towing.
If you do searches you will find topics on revising the ECU programming, installing a different intake manifold assembly, or getting better exhaust flow with a mod for the 'U' pipe that connects the exhaust manifold to the exhaust system. Most of these are a work in progress with no widely available parts or programming services.
There is almost no specific aftermarket performance support for the RL. There are many who have done some great things with the J-series engines, but it's a lot of custom work. The 3.5 liter engine can handle a lot of punishment, but, as was said, the other drivetrain components cannot. The transmission and rear diff unit are designed to handle 300lb/ft of torque max. That doesn't leave a whole lot of room for improvement before you severely hinder the reliability of these expensive parts. The reason the new 2nd gen RL will have a different transmission and rear diff unit is to increase fuel efficiency and handle the extra power delivered by the direct injected 3.5 liter engine. If you're looking to mod a truck for performance, you've chosen the worst candidate imaginable.