It's good for the MMC to advise not to fit a free flow filter as the mid-range high-load fuel map area is likely to be already very weak and this would only exagerrate the problem. But it is simple to assume being able to either control fueling through either injection system chipping or more precise fuel pressure delivery control. Both are  paramount to any upgrade and the combined upgrades will produce all that should be expected from each.

Considering exhaust systems though the standard non-free flow (cat) ones inhibit the engine's ability to breath to such an extent that proportionally, masses of mid-range engine torque is lost. This issue is apparent across the board, fuel-injected 4s, 6s, and 8s.

Getting much more from modern Morgans is not difficult when you begin to understand the underlying issues.