Dusted

hey i have an 85 gsl se and ive had an idle issue for a while, it will rev up and down from about 200rpms to 900rpms it only does it sometimes thought, also since i put in my racing beat exhaust when i start it cold it will shoot up to 3000rpms and stay as it warms up slowly go down i was wondering if it was maybe a tps issue and if so is there a way to adjust it without haveing another tps to make that adjust tool?