Well, it is Custom Intelligence authorities' LEGITIMATE RIGHT to check any 'suspicious' vehicle; although, they need bedisplay/show their credentials and not to be rude or misbehave.
However, I always wonder that how come in a country:
Where the per capita income is < $900 per annum;
Sixty % of the population lives below poverty line;
Which is ranked almost at the bottom of Human Index;
Where the actual literacy rate is hardly 25% (even Srilanka has 80%+) and,
Where the inflation rose to 20% in the last quarter
people have got enough resources to buy luxury vehicles Mercs, BMWs, LCs? Certainly, apart from the very very few, its all BLACK MONEY; earned from illegal/illigitimate means like tax evasion, black marketing, fraud etc. Its all because of such people that we, the tax payers (I pay IT in SIX FIGURES) have to bear the brunt and wrath of the government and the retailers. They do serve u right