2011 Range Rover sport supercharged. truck has 140k miles on it. Had a rough idle and a few random misfires on cold startup. Also the rpms were surging at a consistent speed but was only every so slightly but can def feel and hear it. Always drove great. Very little hesitation, still had its power. I just had a intake valve cleaning done,(walnut blasting) and all new spark plugs. I had replaced injectors and timing chain in past and for now the misfires are gone and also it took care of rough idle. I still have engine surging ever so slightly. Mechanic wants to replace transmission and says that will solve case. Any thoughts on this? Also i deleted cats and straight piped. Sounds amazing. Any other mods for performance as well does anyone know about. Thanks in advance.