The top of the engine should have an engine code stamped on it. The Haynes manual say codes that start in W, EA or EB are 1.7 liter; EC and AN codes are 1.8 liter; GA and GB codes are 2.0 liter. That should tell you what it was when it left the factory. They are all good engines that allow for quite a bit of part swapping to build a multitude of combinations.
You can take a tour of this web site and find out more: http://tunacan.net/t4/
You should be able to identify the heads (1.7, 1.8, 2.0)(from part numbers, or number of studs at the intake) and see if they match the engine codes.