It's real knock. What's your A/F ?
I personally was not that impressed with the E-85 for a non intercooled setup. It seemed to vary too much tank to tank. I always had KR issue on and off because I had no IC.
That is the biggest cause of the KR plus the exhaust backpressure. I had better results with methanol injection and AV gas. AV gas is pretty cheap, just a little more expensive than 94 octane for us.
Could run a 2.6 pulley all day with no knock, and it was a monster for a M90 !
The E-85 could not run the 2.6 pulley with no IC and no headers and no Cams. But AV gas plus Meth... no problems..
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