Help me diagnose this KR

[IDRIVEAG8GT]

Gave it a try yesterday, and even at .82 lambda, the engine rattled with only 20* at 5100rpm or so. i backed the timing down to 17-18* and is all good again. So that KR in my logs is not fake, i could hear it too. Damn it.

Makes me wonder if the cats are starting to get plugged ? what other mechanical conditions can induce knock ?

Car runs good otherwise with less timing, i'm behind .1-.2 sec slower than other G8's with LT's and CAI at the same track, but damn it, i can't believe i need to run baby timing when a lot of other G8's seems to do fine with 20-23* in the same area.

Definitely could be a cat issue. Unless! You need to go one step colder on your spark plugs. Food for thought.

[bluegoat06]

I did that already. I can't go higher than 18* with TR5's or TR6's. i ran TR6's for 20k miles. perhaps the 91 octane here in Southern Cali simply sucks, perhaps the cats are getting messed up. in any case, i don't feel engine grasping for power at all.

[rynez06]

i can generally get about 22 degrees and 19-20 ish at peak torque in these cars...i generally run them at .84-.85 lambda max on these cars, the stock cam produces alot of dynamic compression