If only there were aftermarket exhausts with well designed rear bimodal mufflers that produce a better throatier V8 sound that is quiet when closed and more mean V8 deep throat when open, that would be the go (my aural preference - don’t like tinny sound).
As I mentioned previously in the thread, I've built and modified exhausts since 1978 as a passion that's still active today. Despite the bimodal being louder and sounding more like a V8 should sound, the note in my ears is tinny, raspy and not good enough for me to like and retain. From experience, you need big rear mufflers on any car that are perforated tube fibreglass packed to get the smooth deep note with the minimum of drone and stock bimodal can's are a good size. Starting from scratch, I'd probably roll up a can 8" in diameter 14" long. Most aftermarket exhausts I think aren't using big enough rear muffler cans. Noise level I adjust in the midpipe and I've found with an X or H pipe, the VE/VF 2.5" exhausts need only two hot dog like resonators in the midpipe.
I didn't reinvent the wheel with my bimodal modification and simply used the old open chamber Lukey design. Lukey mufflers in the day produced the best notes and over the years, I've cut many open to discover why they sound the best. Here's the bimodal and I'll explain what I did to mine.
I left the inlet side of the muffler stock, it's 2.25" perforated tube with fibreglass packing in the first chamber. The straight (unperforated) pipe I cut out of the muffler and replaced it with twin 2" perforated tube. The centre chamber I left fully open to act as a Helmholtz resonator and open collector for the dual outlets and the outlet chamber I packed with fibreglass. It's exactly the same design as the original Lukey single inlet dual outlet mufflers we can't buy anymore and sounds just as good, super smooth and deep.
Twin 2" flows the equivalent of a 2 5/8" single pipe, so a twin 2" outlet is ample and flows more than a 2.5" single and with the valves open, the muffler functions like a 2.5" straight through. With the valves closed adds restriction maximising the Helmholtz effect in the centre chamber and stepping down to a 2" outlet, reduces noise quite considerably. It's not as quiet as a stock bimodal with the valves closed but quiet enough to be perceived stock for a V8. Sounds pretty much stock inside the car with no drone.
Normally I wouldn't bother with bimodals and I'd configure the exhaust to optimally function and sound good permanently that's not overly loud. I played around with the bimodals because they're already an OEM fitment and configuring a V8 bimodal is an exercise I had done before. I've done several BMW's however their bimodals are mostly transverse mufflers entirely different to the Holden setup with loud and raspy 6 cylinder turbo notes to improve and control, a different ball game to the trusty V8!
This would be worth a try starting from scratch using full length perforated tubes with fibreglass packing with an external bypass at the rear of the muffler. The valved side is 2.5" straight through and the bypass "quite mode" is 1.75" straight through. You could incorporate a Helmholtz chamber on the quiet side only if the muffler body is big enough.