The Model 1200 loader utilized the tractors hydraulic pump. Relief pressure was set to 1600 lbs, lift capacity 800lbs and a flow rate of 3.7gpm.
The optional, external hydraulic pump drive kits were available for the BF900, K490, K790, K795, K830 and K890 loaders.
These kits chimed out anywhere from 12.5-21.0 gpm. Oh ya, that'll speed your loader up!
The update refered to was a running production change made to the hydraulic pump at the time of tractor manufacture, that kicked up the gpm. TSB#10-81 refrences this and although it was specific to the L-245, the pump was shared between the two.
3.7gpm should be plenty of flow to provide good loader operation. Make sure your tractors hydraulic filter/screen is clean, the hoses don't leak, there are no leaks at the contrrol valve, and that the hydraulic oil is clean and fresh.
If that fails to produce a satisfactory result, then replace the pump.