Knock Retard issue

[Corvette4ever]

Hi all, I have 17 C7 GS A8 running Magnuson Heartbeat S/C at 15 psi. Engine is built with forged bottom end and TSP heads/LPE GT35 cam & Katech 103mm TB

I've been chasing a knock retard issue that always happens at the top of 5th gear. I even tried it with few gallons of unleaded 109 octane added with no help

Today I tried running with an off-road x-pipe with same results. I am using Brisk RR12S spark plugs with 0.028 gap.

In addition, you'll see that I am getting WOT shift flare from 4-5

Logs and Tune are attached. Would appreciate any opinion if this can be fixed from a revised tune

Thanks,

[Ghostnotes]

Log/Check your fuel pressure on high and low side see if you have any drops.

[irun4cops]

Log/Check your fuel pressure on high and low side see if you have any drops.

your guess is correct. The cars require more fuel at the top of 5th than they do all the previous gears. Since people don't have an issue in the first 4 gears, they assume fuel pressure cant be the culprit, but it always is in the OP's above described scenario. Car is running lean. Low side fuel pump pressure will be below 61psi instead of at 70psi.