Intermittent throttle/acceleration issues

My 2006 has started to slowly get acceleration issues. It is hard to describe. It started at low speeds. Usually in the morning when I left for work out of my neighborhood. I would start driving slowly, and without changing my foot on the pedal, my car would decelerate and then speed back up on a regular basis. The scary thing is that it would keep me from being able to pull out in traffic every now and then. Now it has started to do it at higher speeds when I am trying to get on an on ramp. It is much more subtle there. I only notice because of my experience at slower speeds. I had an "engine failed to start" alarm but it was a while ago and has not come back. But the issue is still there. I cannot tell if it actually is the engine not coming on at the right time, but that is the way I am leaning. I tried to look around for possible similar posts, but it is not easy to describe the problem. Any ideas, or links?

 

220K
No warning lights or check engine light as of now. I have not had one on for at least a month.
The filter is new, mass flow and throttle body were cleaned one month ago. I was hoping that would be the problem. The only thing I have not done is change the spark plugs.

 

Should I hide my face when I say no?

 

Will I be able to get the plugs at any regular auto supply store? I will do that today. I know they are iridium. Should I stick with a brand?

 

My preference would be to buy them on Amazon. I have been burned buying some parts on line like the headlamps. What a rip off. It was almost impossible to get the real thing on line. Would you have experience knowing if that has happened with plugs?

 

Man, you guys are making me feel bad. But I did buy the car used. So with any luck, they were changed before I bought it. It had 180K on it when I got it, so I can only hope someone changed them before now.

 

To be honest, I really don't think that is the problem. It seems to me to be a computer problem. To me it seems the engine is not coming on at the right time when it is called for so the electric motor does not give enough juice since it thinks the engine should be on. That is just my theory.

 

I would love to replace the ECU. Can't imagine what that process is like. Yes, the 'engine fail to start' generated a code, but it was cleared by my mechanic when we tried to get it to do it again without success. So even though it makes sense that whatever caused the code is still my problem, it is not causing an error code any longer.

 

Possibly. Still feels electronic to me. I guess this is not a problem that comes up? I have been looking around PriusChat and discovered similar issues. But there have been many different diagnosis. And all issues have come with error codes. I might not be able to get this solved unless my car tells me what is wrong first. I would just like to strike first if I know what is wrong. Of course, this will bite me at the perfect time