Just thought I'd post an interesting thing I found last night.
I went back up to Auckland (from Tauranga) and decided to record the audio with the inserts out - and to be honest, sounded like crap. Exactly the same as with the inserts in (with an exception). But... played it back on the camera - sounded crap. I played the audio back on a laptop - sounded crap. Played it back on a home theatre system - sounded awesome. It's the one thing with recording audio - it doesn't sound 100% like it does in real life.
So I compared the two, with the insert and without.
Without the insert the exhaust is boomy and quite full of bass notes. When the car is under load and your accelerating, the boominess goes. But there are some notes of rasp, especially under the initial acceleration.
With the insert - no boominess. Sounds pretty quiet, no drone. Under load it's a very, very similar note to having no insert. But with one rather big difference. The exhaust sounds better. I didn't think it would, but when played back on a decent system, it sounds more high endish type of exhaust. Almost as if the insert "focuses" the audio - it's actually clearer and it removes 90% of the rasp.
Performance wise - still like a rocket. I'm concerned about the engine running lean, but the car won't get much action for a bit and then a tune will be done regardless.
Now it's slightly embarrassing - go through this entire process to get large pipes and you end up sticking a muffler insert in to reduce the flow. But I have been looking at different exhaust systems (a lot) and I have noticed a lot of exhaust systems get slimmer the closer you get to the rear. So what I'm attempting now is leaving the insert in, but altering the insert to allow more gases through, but keep the audio tight - if that makes sense.
I was a bit depressed last night before I compared the audio - was actually thinking if I should have left everything stock.
I was actually going to just live with the drone, but once I heard the actual exhaust sound change (ignoring the drone), it was like hearing the old 50's style radio broadcasts suddenly improve to high def quality. Like removing the impurities and noise, but keeping the good stuff.
The bonus - when I want open pipes - just take the insert out and probably keep two tunes - one with the insert, one without.
Note that this is a now a poor mans attempt at fixing the exhaust - I've exhausted my budget really, at least for half a year.
Anyone doing something similar, I would suggest following Tims advice!