It amazes me you have your plugs gapped at .055 and get no KR on S3 in Dab 2/3. 22psi or so?
Well, it definitely seems to run much better with the plugs gapped at .055 and no spark blowout which seems to be why most people gap their plugs down.
Again, I think plenty of dielectric grease, new plugs (copper) every 2 years (8K miles), a decent coil-pack (original since 2003) and decent wires (Mopar since 2005) helps.
Note, with most brands of 91, it surely does get about 4 or 5 KR on the old Aeroforce Scanpro.
But not so if I use Union 76 Unleaded Premium and then it's 0 KR.
I don't think KR is necessarily bad for the car.
KR is Knock Retard which is simply the computer pulling a little timing to avoid knock (silent knock by all accounts).
And it doesn't take long, less than a couple of miles and a couple of WOT pulls for the adaptive to kick the ignition advance timing back up.
Especially at higher RPM's where a little more timing helps cooling a little and also reduces knock.
I'm at a complete loss to explain why this happens with my car.
But I'll take it even if Union 76 Unleaded Premium in the SF Bay Area currently costs $4.45 per gallon.
We don't have much corn around here anyway and if I ran it, I'd have to say adios to the stock S3 tune and S3 injectors too.
As well as the fuel pump, fuel level sender and other bits and pieces which E85 apparently causes problems with.
It's a pump gas, street car which is running perfectly now so no need to change anything - until the next biennial check.