surfer_crx:
Would I be right in thinking then that if you write something to the screen, then write something else without specifying a cursor position that it would write to the first position after the last character that was printed?
Yes. You're right on the money. The only other thing to watch therefore, is if your new value is not as long as a previous one you can end up not overwriting it entirely. Simply including a clear() and printing the headings in the loop() function would ensure that is avoided.
surfer_crx:
As for the text "Manifold Pressure" I'm using a 20 character display so I have 3 spare character spaces.
Of course! Sorry, my presumption was 16x2. 