its hard with a N/A engine mate,

i had a clio 172 cup and it was running 212 bhp when i sold it but spent about £3k on getting it to that, cams, omex ecu, head work, thats why i sold it coz it would go no further without doing something like turbo or throttle bodies.

all you can realy do thats cheep is exhaust, de-cat, filter, and some sort of chip, without spending big bucks,