yeah importing modded cars is fine as long as the RAW is able to changeover the aftermarket parts for those that are present in the evidence package they used. Also the aftermarket parts can't alter the structure of the car that is irreversible (ie hole cut out to fit FMIC).
once you submit a car as being complianced, dotars can inspect the car at their discretion to see if the work carried out is by the book. some workshops take a gamble and put the paperwork in without doin the hard yards, and when they get audited they get into trouble. I've heard of workshop owners closing the roller doors when they've seen an auditer come down the driveway and run out the back door. Most RAWS do it by the book and get by. DOTARS maintains tabs on most RAWS and the ones that get audited regularly are the cowboys of the industry and those that are just starting out.
technically the parts taken off must be destroyed, but the RAW can sell it to a scrapper who then sells it back to the customer etc... as its out of their control.