CUSTOMS officers have seized nearly $5 million worth of heroin, cocaine and ''ice'' in two raids. They seized six kilograms of No 4 heroin and 2 kg of ''ice'' after stopping a car outside the Tate's Cairn Tunnel entrance. Drugs were found in the car and at the two suspects' City One flat. The total haul was valued at $3.7 million. The men, aged 21 and 30, were detained and are expected to be charged later. Meanwhile, a 35-year-old Peruvian-Chinese cook was arrested at Kai Tak airport after allegedly smuggling in 700 grams of powdered cocaine worth $1.26 million on a flight from Japan. Acting Senior Superintendent of the Customs Drug Investigation Bureau, Mr Chow Kwong, said they also seized a bottle of liquid cocaine. ''We seldom seize cocaine, particularly in liquid form, because it is expensive on the black retail market here compared with No 4 heroin. ''The black market retail value of cocaine is $1.8 million per kg compared with $390,000 a kg for No 4 heroin.'' The operation was carried out by the joint intelligence unit of police and customs officers stationed at the airport after the police Narcotics Bureau received a telephone tip-off. The suspected courier was stopped as he was passing the customs checkpoint after arriving from Japan. The 700 grams of cocaine were found in one of three powdered milk tins. The other two contained genuine milk powder. A urine test on the man showed positive for drugs and he was taken to hospital. ''We believe the cocaine had come from South American and was for local consumption,'' said Mr Chow. Concern groups yesterday said cocaine abuse in the territory was limited to an elite class of wealthy high-flyers willing to spend thousands of dollars for a small quantity of the drug. According to the Central Registry on Drug Abuse, cocaine accounted for only 0.4 per cent of all newly reported cases in the first nine months of last year, compared with 0.3 per cent for the same period in 1991. A spokesman for the Narcotics Division described cocaine as ''an insignificant problem''.