I recommend 4-2-2-2 devasto. search and download it. it works very well for united so far as I played united too. also try to buy juan matta and nevan subotic if u can afford. they can be used to rotate nani and ferdinand
my player recommendation for Man Utd if you are going to use this tactic:
GK : Van der saar
DCR : vidic ( he can score quite a number of header's goal if played in this position)
DCL : ferdinand (Subotic is also suitable)
FBR: Rafael (Fabio also suitable)
FBL : evra
MCR : Flecter (anderson also...
this tactic is the great. i've tried it with Man Utd and work really well. i can score up to 7 goals per game. and win every game. this is the heavan tactic!!! thanks mate