Depends what you're looking at achieving, if you want big power then i'd say drop the 2.0ltr in. 1.8's aren't exactly slow as i guess you've gathered, so yeah a Remap would work well. Exhaust system and uprated airfilter/induction kit would release a few more ponies, 10-15 in most cases. Then after that, if you're not wanting the 2.0ltr you could either use some Webber 40 carbs, or even have a word with Jenvey about some throttle bodies, they'll put you up to a good 180-190bhp, maybe more depending what ECU you use, PLUS few things sound as good as a zetec on throttle bodies at full chat.

Hoep this helps a bit.