best to use the search button bud but heres a quick list
4-2-1 manifold - raceland cheap and chearful or supersprint manifold but cost a fair wack
de-cat back pipe
full exhaust systems like kam racing , supersprint , piper ect budget ones like sportex , sniper are decent for the price too
enclosed induction kit
as for combining citroen/peugeot parts
if your inlet port spacing is right you can fit a better bigger inlet manifold from a peugeot 106 rallye
also you can fit a 106 rallye head again if your engine is the right year ect...
best power for price is to fit a bigger engine like a 1.6 8v 90bhp blacktop or 98bhp silvertop from a saxo vtr or a 1.6 16v from a saxo vts both will fit straight in with little mechanical knowledge and theres a fair few guides on here
but best bet is to get de-cat , aftermarket exhaust system , enclosed induction kit , 4-2-1 manifold (raceland) and uprated suspension like spax kits from kam racing , blistien b8 kits are very good , better brakes up front or maybe a disc rear beam from a vt model and you will have a very capable 1.4 buddy
hope i helped