Options for more sound

[rotaryjam]

Ive recently purchased a 997.1 and like the sound but I feel it needs a little extra volume.

I've heard of the gundo mod and also the airbox / Helmholtz resonator hack.

Has anyone had experience with these? I've heard a video of the gundo mod on a 996 and it sounds fantastic but obviously not reversible which is important to me for future resale.

Any other suggestions for getting a little more sound out? I'm not interested in spending lots of money on a new exhaust system so will rule out that.