Well you can hear it from both inside the car and out (windows down and more noticable if your next to something to reflect the sound like a wall etc). It only does it under load (actually driving, not just revving in neutral).
Its not the engine, I am a fully qualified mech so i've checked the engine, it is black on the cylinder head around wer the header joins to the head which i am aware of coz the gaskets leaking. Its more like the sound produced when the baffles in the exhaust are fucked, its just the exhaust is relitivley new and it didnt make the sound untill the header gasket went kaput. as ive said ive ordred a new gasket and while the headers off i mite as well put a better header on, so ive also ordered a DC 4-1 header and i'm hoping that will sort it, if it doesnt the exhaust company (www.mongooseexhausts.com) said they'll replace it warranty anyway, I'm just wandering coz i dont fancy another 30 mile trip for another exhaust!!
cheers for any help!!