http://www.suffolk.police.uk/safetyadvice/roadsafety/knowthelaw/modifications.aspxi also did some checks for other laws and if a police officer pulls you and does his standard checks and finds your noise level a little high he can check electronically the actual sound emitting from your vehicle with their bag of goodies in the backl and if they find it to be near or over 80dbl then he is lawfully allowed to check your CO2 emissions and, if able to, check to see if all sections for the exhaust are in place. If your MOT has said passed on emissions yet hes equipment says not you'll be in breach of the law under Road Traffic Act for driving with out MOT and in driving without an MOT you will not have tax or insurance
on top of that and if the cop is really pissed off he can also charge you under section 59 of the police reform act where your vehicle will fall under "Driving in a manner which is causing/has been causing, or is likely to cause alarm, distress or annoyance to members of the public." which includes noise polution as well
so i'm thinking his arguing has really end him in the deep end or he mouthed off, is exagerating his fine and has had an argument with the missus causing the fine
