Which Exhaust

[Axel-F]

...Everest ups the overboost cut-off very slightly (0.95 from 0.94 IIRC)...

Ah, so everest chips has almost no impact on over-boost control...

Anybody know if there is a difference between Sport CAT and Silencer to control over-boost, I would suspect the sport CAT to be more restrictive to gaz, and therefore to provide better control, isn't it ?

[knoxmotorsports]

I had an issue with my timing. With the base timing set at 16btdc, I got overboost at about 4000rpm, sod all power & the car was not very driveable.
I have now fiddled with the timing & found that at 32btdc the difference is amazing. I get boost creep quite a lot but only get overboost in cold weather & when I'm doing around 6000rpm with my foot hard down, which is not very often at all.

32btdc? Is that your "all-in" timing setting, or at idle? surprised your car even runs if that is at idle.