if your looking into paying for a header and a torquer cam you might want to just look for a 16V at a junk yard or a cheap sidekick in the classifides to do a motor swap. I did the whole upgrading a 1.3L thing with headers, myside harley carb kit, and 2" exhaust and wished I just put that money towards a 16V motor swap.
If you absolutely have no want to get a 16V in the future and really want to beef this 1.3 up then yes go with headers, isky cam, and a 2" exhaust.