from the new MOT rules.
If a vehicle first used before 1 September 2002 is fitted with an engine that's older than the vehicle, you must test it to the standards applicable for the engine. The vehicle presenter must have proof of the age of the engine.
If a vehicle first used on or after 1 September 2002 is fitted with a different engine, you must test it to the emissions standards for the age of the vehicle.
If an engine has been modified in any way, it still has to meet the exhaust emission requirements according to the age of the vehicle.
A personal import must be tested according to its date of first use. However, if you're shown a letter from the vehicle manufacturer proving that the engine doesn't meet British emission standards you must test to the next lower emission standard. For example, a 1995 car first used in Gambia with a letter from the engine manufacturer stating the engine number and showing that the engine can't meet catalyst emission limits, then use the non-cat limits of carbon monoxide (CO) 3.5% and hydrocarbons (HC) 1,200ppm.