While you are about it, add 8.8 grams of ascorbic acid and 6.6 ml of TEA to the liter of working solution without sulfite and check the activity.

Meanwhle, I cut the Metol to 0.01 moles /liter (3.44 grams), used 8.8 grams/l of ascorbic acid and 16.6 grams of sodium metaborate, and the activity is almost what it was with 0.05 moles of Metol.