tune-up worth it???

i currently own a 1986 vw golf gti with 190,000 miles. i was wondering if getting a tune-up is really worth it even tho i really wanna keep it. the tune-up will cost around $400. i was thinking of putting a new engine in it at some point when i get the money but currently she's running fine. does anyone suggest one or the other, save up for the new engine or get the tune-up??? Also i need a new exhaust from the cat to the back and that's gonna cost around $350. any suggestions are greatly appreciated.