Most modern premium fuels have a fuel conditioner/cleaner formulated into them
Every grade of fuel in the modern world does. No more and no less in any grade.
TLR, You Tube "Seafoam." It's fun and it actually cleans the living $hit out of everything from wherever you introduce it into the intake tract, through the combustion chamber and right on through the catalytic converter(s). It's like having your own James Bond smoke screen when you start up after letting it sit in the engine for a while after you get a whole can in there, if your engine runs that long before the fumes overwhelm you.
I doubt your IAC would be affecting codes. Still might be worth unbolting the two little fasteners, removing it and checking to make sure the plunger is clean and cleaning out the passages in the throttle body with a bit of intake cleaner. Just don't be overzealous with the can of cleaner and melt the wax pellet thing in the throttle body or you'll be scouring a junkyard looking for a replacement because you sprayed a whole can in there and wound up with a permanent high idle (no, it wasn't me).
I found one line in one of the above linked articles about premium vs. regular fuel in vehicles that don't require it to be interesting. I believe it was the Honda that actually lost power when run on premium. Must've been a bad day for that car, and nothing else.
Thinking more about the fouling claims I postulated, I suppose it doesn't make a whole lot of sense, beyond the ignition trigger point (spark plug ignition), since it's still a volatile mixture in a very friendly condition. The premium fuel is simply going to resist pre-ignition better, but once ignited, it's flame on. So to speak.
So, how far can I push my Starion 2.6 (1988 auto version) in my 87 Raider with the stock pistons and rods (I think it's 8.0:1) in the stock block before parts come through the sides? Crank is nitrided from the factory, as I recall, and it does have the oil squirters and the car's oil cooler. I've heard rumors of some serious boost on that platform but I don't know anybody who still plays with it anymore. I'll run premium in that one.
I'll also keep premium in the 3.6 DI-DOHC VVT in the Camaro. It was made to run regular 87 octane even at 10.5:1 compression (thanks to the DI), but throwing the conservative 10 psi of boost in at 7000 RPM wouldn't play well with it even with the very safe fuel maps built into the programming of the Delphi ECU. Still gets 30 mpg on the highway, too.
Crude just dropped to around $36 a barrel today, so just fuel up and floor it. But seriously, try Seafoam. Like I said, it's fun.
John B.