Ang alam kong Lancer 89 na muffler eh yung transverse yung muffler. Galing sa driverside yung exhaust, curves to the right into the muffler, and then out the rear of the car on the passenger side for the stock Lancer '89 exhaust.

No way to really tell if that's OK until you try it on and see if it's noisy. Personally if I want to put a modified muffler, I'd want it to idle with a slight hint of aggression. Yung very, very subtle lang yung ugong. Then it would get noisy as you rev the (modified) engine...