458 how to exercise intake manifold flaps?

If you find a person with a Launch tool, with 2 way communication, you can activate the flaps. I have the X431 Pro which can do that. If you are local to me, I would be glad to help you out!
I don't know of any reliable way to activate the flaps on demand without the tool, but if I remember correctly, I think quick moderate jab of the throttle will open the flaps (or close them) for a quick second and then go back to original position. You can mark it with dry erase marker, and put a go pro camera pointing at the flaps as you drive around.

According to my local dealer mechanic, he said that It is common for those 2 flaps to not work, because they are linked together and operated on 1 actuator, so there is a little extra stress on those 2 vs the other single flap. He also mentioned that sometimes they throw a code, and other times they don't. And you will sometimes get a feeling like the car has a slight misfire.

I had a similar issue with my car, and bought the central compensator unit to hopefully fix it. However, something else fixed the issue, so I never used the central compensator unit, and it was special order, so I couldn't return it. I sold the car since then, so I still have the part, and it's brand new still sealed in the box. If you are interested, I have it for sale on e-bay at a substantial discount compared to dealer, or even the cheapest online store. PM me if you have any questions.

 

I had the same issue, you can open them with a long prodding tool, pushing on the arm under the second of those horizontal crossovers. Apply some lubricant first, I used lithium spray, worked ever since.

 

I have a Launch X431 as well and can actuate them if you’re in my area (Nashville)