Timed or manifold vacuum advance?

Really late to the game here but the smallblock 360 in my Duster has unknowingly (by my own mistake) been running off of manifold not timed. This thread had me check and sure enough it was on the drivers side port on a Carter 600 (Edelbrock) instead of the timed port where Carter/Edelbrock say it should be. When I switched it didn't run well like it needed tuned. Not sure why manifold vacuum works so good for me. I drive the hell out of the car and race it once or twice a year when I can afford to. It just screams and doesn't have that hesitation when I slam the pedal from idle but it should on manifold vacuum? So confused now. My Dad always said, "Don't fix it, if it ain't broken" so I'll stay on non timed vacuum for now even though it doesn't make sense