i would have thought air filter and exhaust without a map on a na car would confuse the ecu if anything and run down on a couple of hp.
imo the 1.6 se 8v is a horrible engine. they kept putting them in newer a3s and they're still as flat and unpowerfull. hated it so much made me get rid of my golf in the end to find a 1.8t.
remember driving a 16v in a golf and was much more driveable over rev range with just 5 more horses that was years ago before i drove anything powerfull and only had my 8v

from that moment on i wanted something else haha.