If you have a 3.5 quad cam motor, you need to be running premium to get the gains of actually having the quad cam engine. end thread right there.
I'll dive in a little deeper here for explanations that will help others.
Running 87 octane in your 6G74 is basically forcing itself to de-tune. Costing you power and torque, which you desperately need if you're on this forum, because you're running larger than stock tires.
This applies to ALL of the 6G74 engines SOHC or DOHC, if they have a knock sensor, they adjust timing based on ping, barometric pressure and other inputs. If you're in doubt, check here to see if your truck has a knock sensor:
https://www.rockauto.com/catalog/raframecatalog.php?carcode=1356713&parttype=5108
This engine is equipped with a knock sensor and aggressive timing maps in the ECU. When you run 87, it detects ping and it retards the timing. In these engines, much like other japanese NA engines of similar era, timing and flow are everything. Advanced timing makes for more power, the farther you can advance timing without getting ping, the more power you make. If you're running 33's and 87 octane, you're probably getting somewhat tolerable MPG's, if you're running 35's you're probably getting pretty bad, so the logic usually says it doesnt matter what you dump into it, it's just going to drink it fast. But that's not true. If you run higher octane, timing advances further, more power and torque is supplied, the engine works less to move those big *** tires and you end up with better fuel economy. So if you have access to 93, 95, 100 unleaded, run that stuff and let that engine scream. It was designed for a turbocharged sports car for god sake, it wants to hit red line and it wants it often. These ECU's are tuned fat(rich) for safety, you can piggy back an S-AFC with a wide band and tune them to get even better MPG and make even more power, at your own risk. Or you can take it to a good mitsu tuner, it's no different than tuning the 6G72 quad cam found in the 3kgt naturally aspirated cars.
Disclaimer: since some people have almost zero actual automotive performance knowledge, i think it's important to note that if you choose to bump up your octane, you need to reset your ECU, the ecu will need to run for a few hundred miles through various throttle, load and gear situations to work out the long term fuel trim, and might die around town for the first few days as you come to a stop, it has to re-learn.
