An average of about 40 motorists were caught each day for illegally modifying their vehicles in the first six months of this year.
Their infringements include modifications to exhausts, lights and adding tinted windows, which are against the law.
Latest figures from the Land Transport Authority (LTA) show that there were an average of 1,240 cases a month from January to June - almost 10 times the 146 monthly average in 2008.
An LTA spokesman attributed the increase in the number of vehicle owners nabbed for such offences to stepped-up enforcement and more tip-offs received from the public.
Safety, said the spokesman, remains the key reason for such regulations.
Illegal modifications, especially to a vehicle's exhaust system, for instance, may result in the inability of other vehicle components such as the brakes and steering to cope with the additional power, which may compromise the vehicle's safety.
Changes to the Road Traffic Act last November now allow the LTA to apply to the courts to detain illegally modified vehicles for up to three months when their owners are convicted.
But this is only for "aggravated or repeated infringements", said the LTA.
Some modifications to parts like exhaust systems, engines and transmissions are still allowed, but only if they have the LTA's approval.
For instance, modifications involving after-market exhaust systems are allowed, if they have undergone testing either by the vehicle manufacturer or independent test laboratories, and are certified to comply with internationally recognised standards on safety and emissions.
As of last September, the LTA has approved 81 aftermarket exhaust systems.
Motorists who "pimp" their cars or motorcycles risk getting the warranties for their vehicles voided. It may also affect insurance claims.
Those found guilty of illegally modifying their vehicles can be fined up to $1,000 or jailed for not more than three months.
Repeat offenders may get double the penalty.
Despite these downsides, some motorists still spend hundreds and thousands of dollars "pimping up their rides".
Most believe that if they drive safely, modifying vehicles will not pose a danger to other road users.
A 26-year-old motorist, who did not want to be named, said he does not believe there is anything wrong with his illegal modifications.
"It's to increase the performance of my car, I don't think it will harm my car," said the owner of a Mitsubishi Lancer. "Plus it's cheaper than the original parts. After all, it's about the person behind the wheel."
Chairman of the Government Parliamentary Committee for Transport, Mr Cedric Foo, disagrees.
He said illegally modified vehicles not only endanger other road users but they are also not environmentally friendly and "LTA should look at workshops to make sure they don't sell illegal parts, or provide illegal modifications".