I'm a ham (Amateur Extra, KD8..., send me a private message if you want my full callsign).
This is a standard warning that every manufacturer puts in their cars. Actually, no all manufacturers, only those who consider the installation of a transceiver a real possibility, other simply don't bother to check.
I have run all kinds of radios (HF, VHF, UHF) in my Toyotas (several of them, not RAV), up to 100W HF and 50W VHF/UHF without any issues. As long as you install the radio properly, there should be no problems.
Key electronics like the engine and body ECUs are well shielded and "industrial" grade, much more hardened than household electronics.
The only things I would be concerned is running your coax or placing the antenna too close to an ECU, key sensors (like ones that control airbags or VSC) and airbags inflators. Although the probability of having a problem is low, you wouldn't want an airbag to go off when you key the mike. Or have the VSC kick-in when not necessary.
Find out where all the different sensors are and stay clear of them. For example, the yaw sensor that senses turn ratio / acceleration and provides input to the VSC (and indirectly airbag ECU) is located between front seats, more or less under the hand brake lever. This is just one example. Airbag collision sensors are mounted in the doors (several of them) and the front of the car. Don't know where the rollover sensor is in the RAV. You may want to get a full "map" of all the different collision and VSC sensors, as well as the different ECUs and airbag inflators, and route the coax at least 4-5 inches away. For example, my FJ cruiser had 5 different ECUs and over a dozen collision / VSC sensors, and some locations are not obvious.
