i want to replace my standard centre and back box for decat centre and louder bb. will i get a big improvement in performance or is it best to change air filter aswell?
the car is a standard MY97 turbo.

will my standard ecu be ok with these basic mods.

 

Centre and back box won't give any big gains, but will probably make the car feel a little more willing to hit the rev limiter. A filter may give a touch more throttle response.
ECU will be fine