I recently had my head gasket, exhaust manifold gasket, and cat replaced at the dealer. When I got the car back I noticed when I'm driving if I accelerate say to change lanes or just to speed up. Weather I down shift or not the engine sputters as if it's being staveres of fuel or it just doesn't have the balls. It's a shake strong enough to jerk the car. Not enough to break you neck but enough to rock you in your seat. I've tried Seafoam in the fuel and oil and I've stepped up to the highest quality gas. I've check my spark plugs all of which are fine. If anyone else has some insite please comment below. Thank you.