My toro groundsmaster 72" mulching deck always bogs down in grass over 4" tall. Someone said there is a way to modify the deck so it will cut better. I would be interested even if it doesn't mulch as well. Any ideas?

ANY mulching mower is going to bog down in tall grass. THey are intended to be used before the grass has grown tall enough to hide small pets in. (thats not literal, just making a point)