misfire at mostly at low rpm and under some load. Had coils changed, tune up, fuel injectors cleaned, still exists. It shakes car. It can feel like motor mount but it is not. It is the SHO
How many miles on it? Is the check engine light on? What was included in the “tune up” ? New spark plugs and… what else?
How about having a mechanic ride in the car with a scanner connected while you show them the misfire. That way he can identify the problem rather than just tossing parts at the car. Expect to pay for his time but you will be dollars ahead in the long run.