the reason you can't find a header is because they don't make them, you can have one fabricated at a local muffler shop or machine shop but u better have the bucks to have that done. www.nopi.com
has a good catback exhaust system made from pacesetter for a good price. but when you are searching for the exhaust search under 1990/ mitsubishi/ eclipse. for some reason there is more parts listed for the for that make and model which i don't know why since the engines and everything is idenical except alittle body diferences. oh and any 2.0L fwd 90-94 catback exhaust will fit the 1.8L.