Are you flooring it or just driving casually while towing . I was towing my boat and gunned it and yeah the egts went way high but driving normal it wont go that high. If your not driving crazy then I think you might have a leak. I drive 14 miles on steep hills and my egts would go to 1300 1400 in overdrive going up my hill. Highest it hits know is 1200 in overdrive at low rpms.
I hope this helps you out.

EGT HIGH
 

My foot is in it hard!