and after market exhausts can become a touch louder or boomer if the packing inside settles with age. It's possible the previous owner went down the S/S sports exhaust route and you have one of those.
The standard rear silencer was fairly restrictive back in the day and mine only lasted a couple of years on a car that covered 12,000 miles a year. I cut an old one up and there were a number of baffles making the gases change direction.
From tuning articles back in the day, fitting a less restrictive exhaust system and / or a less restrictive air filter like a K&N changes the carburettors view of the engine. This would have required a change of metering needles in the carb's to keep on top of the fuelling mixture and released a few extra bhp that these mods bring. I posted an article about Triumphtune a few years ago which detailed these, Triumph Over Adversity.
No question too stupid, unless it comes from me
