Hi giys

i want to change my back box back to the oem sti one for a 97 sti.
Problem is the car has a 3” japspeed decat exists right through.
What is the most logical way to fit the sti back box with a 2.5”?? Bore to the 3” middle section pipe?

Is this even possible?

Just looking at what hat my options are but would love be the standard box back on without ripping off the whole system.

car is mapped to the japspeed system so the minjnal disruption to flow the better

Superb! Thanks!