Engine Vibration/misfire possible reasons

Hello,

I have terrible vibrations on my 2011 prius. The thing is so terrible that in some moments I feel like whole car is falling apart.Vibrations only take place when electric power is not enough and ICE kicks in and you just try to maintain the rpm-s, as far as you floor it or just release the throttle vibrations disappear.

First, I though it was all engine mounts' fault, I checked and re-tightended them all y'day. vibrations still persisted.Then I put my car on diagnostics.also had no check engine light. What I found was misfire on cyl 1. I changed all spark plugs today and while I was down to it switched 1 and 2nd coils for plugs. when I rechecked the diagnostics, misfire was still there on 1st cyl,so it means issue is still in 1st cyl, despite plugs being new and coils changed. Tomorrow I am going to check compression on all 4 cyl-s and see if there is a mechanical problem with the 1st one, by that time is there anything I can check? I was thinking of fuel nozzles, but want to check compression first.

Could you please tell me any other items I could check?

Thanks in advance

 

107 miles. The intake is brand new, as the previous one was cracked after accident. I checked trouble codes on TIS techsream and it did not show EGR malfunction,I did not check it manually though

 

little update.Although when I bought new (read "second hand") intake, it did look clean, I dismantled it as suggested and thoroughly cleaned the whole system, starting from EGR pipe and ending up to intake valves.Second reason I also was not lazy going that far is that I suspected that small piece of older intake fell between intake valve and its seat and wanted to check if there was any issue with that.if you have not stripped intake before I should mention that you can clearly see intake valves, even without boroscope which I kept in handy Long word short, I cleaned intake first with jet stream of water and afterwards by gunk remover spray,although it looked clean, there was lots of tar inside, especially on EGR line and as 1st cylinder is the furthermost its EGR line was the dirtiest and clogged.Afterwards I reassembled everything and car had no vibrations ever since, even with old spark plugs on (later I reinstalled the new ones).

hope my experience will be helpful for some users here.

P.S. Sorry could not take pix, as I was too dirty

 

Thanks for the help,man!