sx90seca

hey i just bought a 1990 ae93 4age 16v (pretty sure) and my exhaust sounds really tinny. seems like its coming from the flex joiner up the front end. any quick/easy fix's? or should i just save some cash and do my exhaust up (extractors, high flow cat. etc.). also my brakes are stiff as would that be pads, lines or sumthing else? i also need a new central locking switch easiest place to find 1?