You're talking ambient temps here, so intake temps. Intercoolers won't do squat against that, you need a decent cold air intake. If you're thinking of the type of system that uses a cone filter somewhere in the wing or behind the bumper vents, make sure you get a 'sock' for the filter or you risk sucking in water. Hydraulic lock is very messy!
there is no chance I take the cover off the engine.
Carbonio would be maximum I'd go for.
But if neither IC nor Carbonio offer much help for the problem at hand (which is - feeling of slower acceleration when ambient temp is high) then I see no point in installing them. Now it is Autumn, I wonder what the car will feel like in Summer, when it is not 19 but 29 degrees outside. I also wonder if the map is more of a problem (in terms of reduced engine/turbine lifespan) than fun-factor at those Summer temps.
