intermittent momentary stalling

My prius started doing something weird yesterday and I am hoping someone has seen this before. I am a good mechanic but new to hybrids. The car once in a while acts like it stalls, usually at freeway speeds. The car will have no power and the check engine light pops on and then a second or two later goes back off and the power is back. No codes are stored. My guess is it is stalling for a moment then picks back up. It usually takes anywhere from 1-5 seconds to recover, but never stored any codes.
I don't think it is electrical as the radio, lights, and all other dashboard lights continue working properly. I am thinking something fuel related. It seems checking pressure is difficult in these cars and where the problem is so intermittent it would be hard to just test anyway. My ideas are

Failing fuel pump,
Failing fuel pump relay
Fuel Filter (I believe it is in the tank?)
Fuel Pressure Regulator
Just a bad tank of gas

As I said I hope someone has had a similar experience and can point me in the right direction or give me your thoughts.

 

140,000. I guess that is possible but the engine light does not stay on either, it goes off as soon as the motor engages again. Thats what lead me to believe that it was a stall. My guess is the light comes on just because the motor stalled, as if the car was in on mode rather than ready.

 

Innova 3040. It has read codes from this prius before. I just don't think a code is being generated.

 

It was cleaned 3 months ago when the head gasket was replaced. It has ran great ever since. And it still runs great except for the intermittent stall.

 

I realized that I never reported back on this in case someone else has the same problem, here it is. I discovered a loose ground connection on the valve cover. There are 2 ground wires that attach on the top of the valve cover. One came loose, I assume this send low voltage to either the fuel pump relay or to the ECM. Cleaned up and reconnected and no more issues.