If you fit the 'long primaries' Caterham 4-1 exhaust system then you will need to make a bigger hole in the sideskin. My engine happily made nearly 240bhp on that exhaust, so it's obviously suitable for quite a long upgrade path although you'll get much better midrange (from a high state of tune at least) with a 4-2-1.
1.4K Supersports were fitted with a different (bigger, aluminium) plenum chamber which may or may not have included a different throttle body (I don't know). 1.6 and 1.8K Supersports all used the same plastic plenum & throttle body as their non-Supersport variants.
Mike