Damn Knock

[91 TSI ZzZz]

Okay damn it... I had a good fuel trim when I bought the car so there was no knock on my car at the time... I had the lo and hi throttle #'s written down by the by. So when I switched my trims for 100 octane I could change the fuel settings and change them back when I go back to 91 octane gas. But when I switched the #'s back I had 43 counts of knock!! wtf I kno that the trims cant ever be the same when u switch but seriously how do I go from great to worst with the same #'s?
I have to retune it obviously with my data logger but if anyone can explain why this happened please do so and it would be greatly appreciated

 

[SBstar]

what were you using to record knock?

 

[eldiabloz13]

Theres been accounts of this happening before in another post i just coulden't find it.Now one of the reasons may have been since you were running such a high octane and then going back to reg fuel that its still might run rich.Keep in mind 100oc is pure as hell and needs time to completly burn off.So adjusting it back to the #'s maybe not gave it enough time to burn it all. So you might have to adjust for a high octane for a couple days.If that dosent work just check it with the logger you said and that should tell you exactly whats going on.