mate it seems you haven't listed any modifications on your car that would make it worth your while getting engineering approval.
it's expensive (and painful), for a start;
you will have to lower the exhaust volume, raise the car to the minimum legal height, remove the tint and reapply legal stuff, etc, etc, just to get the engineer to even look at it.
engineering certificates (sadly!) don't provide you with exception or extra allowance for noise and height limits etc