To me it sounds like a fuel issue. Have you ever had the fuel pump changed? If you smelled gas there may be a small hole in the fuel line. The cause of the loss of power could be air in the line. If it small enough it could only accumulate air while it sits. When the air reaches the engine. Boom problem. But while you are driving the pressure the fuel pump creates is enough to keep from being sucked in. Does this help?
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