[spuggy]

Your car may not have seen 1.2 bar, the tell-tale could have just been set/left there. Only the previous owner knows for sure...

930's often seem to run fine with broken rings, I'm told. Many factors are in play for detonation; timing, fuel, overboost are all suspects, the lower you can keep the temperatures the better - so intercooler/shrouding is a factor as well.

My car had no broken rings - but showed the tell-tale tiny pockmarks when apart for a re-seal. I fitted a J&S Safeguard, mostly to protect against a clogged injector or a bad tank of gas. It instantly showed when my dizzie stopped returning from full advance (giving me 28 degrees at idle) months later and it had to work for a living pulling timing...

Seems to be a very sound investment to protect a CIS (or even Motronic) motor. even if you keep everything entirely stock; all my knock is below 3500 RPM, even on the track. When I reverted to my original RoW distributor with the Safeguard fitted, it was also very noticeable how much more knock was detected/prevented, even with stock timing. RoW springs have a much more aggressive advance curve.

You can also use it to run more aggressive timing than stock to enhance cruise economy/off-boost response, bleed timing off as boost comes in, and still provide adaptive per-cylinder knock control/protection. My 930/60 currently runs 34 degrees mech advance @ 4000, and uses the Safeguard's boost retard to bleed off timing back to RoW spec (28 degrees) at full (.8 bar) boost, keeping 20 degrees in-hand for knock retard if necessary (it usually isn't, but it sometimes pulls as much as 4-8 degrees @ ~2800 RPM climbing hills, before the boost retard threshold - mine is set to 0 PSI - is reached).

Low to mid range response seems considerably improved.

There's a Safeguard unit designed for coil-on-plug; I'll be getting one when I go that way.