Mine is not as severe.
Interesting problem and solution. I have a 7 and the cube is "soft" mounted at the sump attachment under the M1B spider. Schematically, after the servo and before the spider. I notice over 10k that as leaned the fuel flow wanders with 0.6 GPH above and below a mean, the engine can begin to stumble on the low side, so the change appears real. I have measured fuel temperatures and found the highest rise (for my installation) was between the boost pump exit and the inlet to the mechanical pump. In the tunnel seems to be pickup the heat.
I am clearly approaching the issue as a temperature problem, not a cube vibration, but the 14s seem to have a flow inaccuracy I don't have.
This gives me another avenue of thought, thanks to the OP for launching the conversation.
Last edited by BillL : 05-19-2020 at 11:25 AM.