Possibly in part due to diff ratios used but I have chased a lightly tuned 1800 4/4 owned by a friend and whilst I have more outright power there was very little difference in real world performance. I have to say I was quite surprised.
I wonder if that was the eason why Ford added the restriction to the 1.8 throttle body. Perhaps it was just a marketing thing because the 1.8 and 2.0 products were just too close.
PS - I think they both share a 3.73:1 diff ratio