It's lazy policing to pick on modified cars.
I've found it helps to be a little older,(IE not a punk kid) and a lot smarter than mr plod. Manors go quite a long way to. I got pulled over at a check point, (In my old RB20E A31 cefiro sh1tter) and asked to open the hood. The cop poured over it looking for a wastegate with screamer pipe. (They did an training push, teaching cops what to look for)
It wasn't even a turbo.
There's been reports recently of cops here being complete arseholes. ticketing people for things they haven't even done, and in some cases inpounding cars over it. Cops like that do nothing for the police image. (In the same way that dickheads don't help the rswt of us car enthusiests)