I don't know how the engine is in an MX5 but I certainly noticed in my 2014 GDI Plus 4 the gearbox is canted over with the filler/level plug lower than the horizontal. I just raised the pads on one side of the two-post lift and lowered them on the other side to get the box more or less level. I then filled with Fuchs Titan Race 75-90 full ester sythetic gear oil. After the change I too thought the gear change was improved - though whether this was my imagination, the improvement in the oil quality over the original or the higher oil level in the box I don't know.
