I have an RB axle back exhaust installed on my 15 Mazda 3 iGT. My car is also lowered with CS springs. When I first had my mods installed I noticed a little bit of a burning plastic / chemical smell after driving hard / hard acceleration. It seems to have decreased with time / mileage but I still get the smell, and it is smell able from the cabin with the windows down after hard acceleration. Any idea what this might be? I'm a little concerned.