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There are quite a few things that could potentially cause your symptoms. Even though the engine light hasn't come on the first thing I would recommend is checking for fault codes. There could be a code or one trip failure setting when this happens yet the engine light isn't turning on.
If it won't set a code then it will really need to be diagnosed by watching data while the problem is happening. Another option would be to install a data recorder on it and then a technician can play back data that happened during the event at the shop on a computer.
Possible causes could include low fuel pressure, upstream oxygen sensors, MAF sensor, a limp-in due to lack of cam or crank signal, or ignition issues, but based on your description it sounds like you may have an electronic throttle control issue. This engine uses electronic throttle control where a sensor tells the ECM how far the throttle is open and then it controls the throttle body accordingly. There's a good chance the throttle body itself is causing this.