I’ve had my hand tuning numerous vehicles. Via standalones, piggybacks, and flashing OEM ECU’s (where possible). I’ve tuned my share of modded N/A and turbo’d Lexus’s (Lexi?), including my own supra twin turbo swapped 6-speed IS300. I moonlight tuning my personal Porsche 911 Turbo, to a safe 650hp. I’ll say I’m slightly qualified in this matter.
Toyota ECU’s are notoriously locked down. In the decades of someone being “close” to reverse engineering their ECU’s, I have yet to see a flasher on the market to directly tune their ECU’s. Honda’s have it with Hondata; Cobb tuners for subbies, Porches, BMW; Bully Dog for Nissan, Ford’s, etc. And many more that I did not list. But actual flash tuning for Toyota? I haven’t looked in a couple years but I still believe it’s unobtanium.
Which means one has to resort to piggybacks like Unichips. These are a much more expensive and an involved to install proposition.
That said, for N/A motors, there’s really not much additional performance on the table. At least without long term durability compromises, as OEM tune their motors to a high degree. For fuel efficiency and emissions, but that’s generally aligned with performance.
Engine tuning boils down to ignition timing and fueling. One can gain HP via advancing ignition or leaning out air/fuel. Again, not much more safe HP on the table with ignition, unless one wants to walk into the margin area where there is increased pre-ignition, knock, and stress on rods. Fueling is generally where tuners make more of their HP. They tend to run fueling leaner. So instead of air/fuel ratio’s in the 10:1 or close to 11:1 boundary, they may lean it out to 11.5:1. The actual values depend on the motor and rpm/load. But generally, they will lean things out. This always causes the motor to run hotter. Which again, walks closer to the pre-ignition/knock boundary, and potentially compromising long term durability.
The one honest hp gain here is a tune which takes advantage of higher octane. This allows tuning to legitimately run advanced timing, without getting into the marginal safe area. But one would also have to commit to always running 91/93 octane, unless there is a tune switch that allows one to switch back and forth.
Mat at OVTune has cracked the crypto issue for 3rd Gen Tacoma ECUs. His product is a direct flash to the ECU via cable and laptop. I flashed my 2017 Tacoma with a 91 min Octane tune and saw definate performance gains in addition to changes to throttle mapping, etc. Make highway driving in the 3.5 much better.