If your sled has the Walker Evans shocks it is likely they need to be recharged.
Are you actually trying to steer the sled with the handlebars in an upright position? If this is the case you will experience "push" and the sled will fight you. In deep snow these sleds are controlled by transferring your body weight slightly from side to side. If you want to go left apply more weight to that running board. Look in the direction you want to go. Also emphasize your body towards that direction as well.
The idea is more or less to tip the sled on it's side. This allows the sled to create it's own berm so to speak. When doing this also turn the handlebars the opposite direction you want to go. I know its counter intuitive, but it works. You will hear people refer to it as counter steering.
I found the Holz front end to be much more predictable than stock, but that is an investment. You might try moving the front shock of the rear suspension into the lower position. This gives better track angle for getting up on the snow, but might also give you a more positive feel in the handling. Hope that helps.