Hi guys, what is the most engine upgrade that have the most increase in HP & torque, without somebody realized the car is modified by the sound of its exhaust?
As far as I know is installed the tuning box such as racechip, or ECU remap such as apr stage 1. Apr stage 2 as far is I know require replacement to the downpipe that will change a little bit of the ''car sound''.
Any thoughts?
If I already have racechip pro 2 in my engine, will it have so much increase when I change to APR stage 1?

Thanks

It's not a volkswagen, it's just a car