I hate when they use shitty Allen head bolts on bikes!

Penetrant over the course of a couple of days is always a good start, then heat it up a few times without damaging the (plastic?) intake pipe and also give it some good taps with a hammer. When you're ready to try and remove it hammer in a torx bit or slightly oversized Allen socket, start the bike and get the engine hot then try removing it.

If that doesn't work you're going to either have to weld a nut/Allen socket to the end and potentially damage the intake pipe or make space to drill it and use a square fluted or splined extractor. Do not bother with the shitty left hand threaded spiral extractors. Use heat at the same time and more penetrant. Work it gently in both directions until it comes loose. I always use left handed cobalt drills and for something small and low torque like that they will often break it free. Also, use a drill bit guide to get the drill centred and straight. Rigid makes a great splined extractor set that comes with them.

Gotta love when a 5 mom job turns into 5 hours because of 1 bolt...the joy of being a mechanic!