Whilst I'm here it's time for another update. I've been riding the bike everyday, and it's been good. The backfiring/exploding intake issue was solved with the addition of a relief valve. Now when it's cold and decides to backfire in the intake instead of punching a hole in my intake, the valve just pops open.
I've also put a larger pulley back on it to increase the boost to 25psi. It sounds like a ridiculous amount of boost (I initially only wanted to run 5!) But I'm convinced the high readings from the gauge are not what they seem.
25psi is the pressure readings from my small intake tract. However the motor ought to grenade itself if it was running that amount of boost inside the cylinder. I'm fairly convinced that because the single piston only opens the intake 1 in ever 4 strokes, the pressure in the intake is much higher than what the cylinder sees. This is why when I reduced the pulleys to give me a 10psi boost the performance was barely noticeable. That 10psi might only have been 2psi once the cylinder inhales.
So I've cranked it back up and it's going good. Took the bike on it's first open-road/highway trip with some mates on their sports bikes. It was a hot day and I started getting some detonation.
This was the first time SavageBob has seen sustained boost. i.e. boosting between traffic lights in the city is not the same as continual boost doing 100kmph.
I was running 95 octane. I've now increased that by adding toluene to my tank so it's probably around 98-100 octane now. I'll see how that makes a difference on the open-road next time I get a chance.