[V]

i had mine on my air dam for a while and i was lowered a lot.

yes it is still illegal and you can get in trouble.

39:3-33. Markers; requirements concerning; display of fictitious or wrong numbers, etc.; punishment
39:3-33. The owner of an automobile which is driven on the public highways of this State shall display not less than 12 inches nor more than 48 inches from the ground in a horizontal position, and in such a way as not to swing, an identification mark or marks to be furnished by the division; provided, that if two marks are issued they shall be displayed on the front and rear of the vehicle; and provided, further, that if only one mark is issued it shall be displayed on the rear of the vehicle; and provided, further, that the rear identification mark may be displayed more than 48 inches from the ground on tank trucks, trailers and other commercial vehicles carrying inflammable liquids and on sanitation vehicles which are used to collect, transport and dispose of garbage, solid wastes and refuse. Motorcycles shall also display an identification mark or marks; provided, that if two marks are issued they shall be displayed on the front and rear of the motorcycle; and provided, further, that if only one mark is issued it shall be displayed on the rear of the motorcycle.