Apparent "lugging" under slight load

Lugging is exactly what it felt like to me also. The reason is that any minor misfire which might go unnoticed in a non-Prius engine is greatly exaggerated by the ECU trying to compensate for the misfire at the MG. Once I understood this, it all became clear to me. Suggestions that sounded ridiculous suddenly seemed much less so.

Before doing anything or spending any money you might try disconnecting the EGR connector to see if the problem goes away. If it does then the issue is somewhere in the EGR tract. If there is no change then at least you have ruled out an EGR caused problem and you can look at other things that might be causing a misfire. The reason I didn't pull off my EGR is that it looked to me like it was replaced at some point so I decided to start with the intake instead. Pulling the intake off isn't a bad job at all. I had it off in about 15 minutes mainly because I didn't disconnect the coolant hoses from the throttle body. Cleaning the intake on the other hand was a huge PITA and the amount of crap that came out of it was unbelievable. A new intake online is less than $250 or about $350 at the local dealer. Not a huge expense if you don't want to mess with cleaning it.

 

Update: Been about 16 months since I cleaned the intake. Added another 15,000 miles and still no return of the engine shaking. These cars are amazing.