I Noticed after Having Installed the Memcal, the Rev Is Inclined to Hold When the Clutch Is Depressed rather than Drop Down

It's the nature of the tune, because we modify the cold start maps a little to improve throttle response when the engine is cold.

If you hold the clutch in and keep your foot off the gas the revs will drop, it will just take a little longer than before.

Give it a couple of days and it should settle down as the PCM self learns to suit the new tune.