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)

I was watching NZ motor patrol an tv last night,they pull over a rotory in smick condition.The cop asked to pull the hood and when he sore that it had been done properly he started having a great convo with the owner.Said that it was great that it had been done properly and gave the modified car community a good rep because so many are boggy.

My R100 bp 13b was a nuisance since I owned her was just below decibel limit but didnt stop the canary sticker in the 90s only to always pass at the station. Turbos have changed that for rotaries but the other day young punk was feeling tough and pulled me over for supposedly not stopping on give way which was bull and then tried to tell me my brakes are hot and smelly when it was my rocker cover gasket leaking a drop of oil every so often and smelling a tad but insisted my brakes where overused so I quipped to them that they are "used" especially at give way signs from slowing down from normal road speeds. He backed off since my wife looked off colour at them and made a good witness to my normal relaxed driving. However this area is full of drunken drivers going home from the pub yet they look the other way cause the pub owner surely gives them a handout to keep their business booming as always all the drunkards park a tad up the road and wobble back and forth from their cars where we hear them smash bottles, scuffle in fights and basically wake everyone up at all hours in the morning. Its one pub everyone hates in the area for the D1ckheads that cause all kinds of problems after closing hours 1-3am every night, yet the cops are busy focusing on revenue tactics from harmless commuters.

Yeah i was having problems with p1ssheads walking through our property becuase its quicker to walk in the back lane to the front off me and my flats neighbours which are on the same property.So i put a lock on the gate and it doesnt happen anymore although they f and blind because they get to the gate then have to go around anyway.

The topic has digressed a smidge, but in a great read kinda way!

from what i understand they can defect anything thats been changed from standard and not mod-plated.

Over here, they can defect a vehicle for whatever they deem as being a hazard, regardless of if its factory or a mod., especially if you are giving them attitude. I remember someone getting a yellow sticker for having more than 13 cigarette butts in their ashtray. Reason given: potential fire hazard.

Attitude is everything as some have pointed out,Modifying dashes is generally OK as long as the padded section remains basically stock as this is a safety standard and they reinforce that even more so than simple compliance stuff,\.
Early vehicles only had to comply with standards applicable at the time so Webers on a 1200 are OK,But if you drop in a CA18 then you have to comply to Later Standards applicable to the Engine Year,That is a trap many are not aware of.

Therefore do your research carefully and modify sensible and try to find the increasingly scarce engineer that will sign off on mods so you are covered,An earlier car means less hassles as it has less rules to comply with.

Basic roadworthiness such as minimum height and legal tyres no sharp bits sticking out etc will save you much grief down the track but you can still have a decent nice ride.

Just remember no cars that belong in a Transformeres movie.