For goodness sake, leave her alone, turn the stereo up and you won't hear any more noises ! Things will settle down after a few miles, give your mods a chance to bed in.

Ken
An exhaust blow will never settle down - it will only get worse if not rectified 
OK, your a perfectionist.
I must confess the worst thing about my Omega is I can't hear the engine or any noise its making.
I grew up through a progression of cars, and you got to listen for noises like the engine was clattering, the steering was a bit pulling to one side, or the exhaust was blowing, but with this Megga, I can't hear sod all, apart from the stereo !. Its a bit too quiet, I miss being able to hear how hard the engine is working, or if something is clattering, but modern cars tend to be that way, good for 200,00miles then scrap.
Have you ever changed the distributor or Radiator on an original mini?, now that's fun !.
Don't worry, just enjoy the drive,
Ken
PS We really must go for several pints some night !