I run 4 into 1 extractors with a 1.75 inch exhaust with an 18 inch long straight through resonator and a dynaflow rear muffler. It's really quiet at idle (nearly as quiet as modern cars) but when you give it a bootfull it still sounds ok. Much deeper and better sounding than the standard exhaust - and it gets no attention from the cops.

My a12 is nearly stock, just running a high lift cam and a re-jetted standard carb. Surprisingly, to get the mixtures right we actually reduced the size of the main jet because the engine was running rich. I guess they must run rich stock also?

It is a fun little car to drive - sure not the quickest, but I can get 41mpg cruising at 120 - 130 km/h and it keeps up with modern traffic just fine.