the abf is not easy to get to 200hp without spending major money, the small things you talk of wont relase much at all from the abf, cheapest ive seen is a decat, smoothed airbox & panel filter & then chpped & that reached a respectable 165bhp, but thats as far as the abf will go without spending serious money....
the 1.8t is the most cost effective way to get to 200 hp in a mk3...... ideall you'd want an agu engine code as they are still throttle cable some of the later 1.8t are flybywire and as for engine, audi, vw, seat. they are the same engines...