Performance upgrade on a 1300

What modifications can be made to a 2000 MK1 1300 5-speed to give it a few more Kw's, without changing engines ? Any idea's ?

iv put bike carbs onto mine..but speaking from experience, if you want to keep the car for a long time id just put the money towards a engine transplant because your always gunna want more power and in the end it makes more sense to just save all the money up for a bigger engine insted of blowing it on bits and bobs to make ur standard one better...just my view tho.