If some of the change in cranking compression from the 150-155 range in summer of 2020 (mentioned earlier in the thread) to the more recent 175-185 this fall came from carbon build up. The seafoam should really help.
FWIW..Dropping the spark plug heat range will help a bit, but will have a pretty limited effect since a 43 is already fairly cold. If your not using a wide band O2 sensor and judging jetting from only reading spark plugs the colder plug will make the jetting change more obvious. As hot as the plug are burning now it is not going to be very easy to read plugs and make jetting changes. I doubt the AFR is very far off, as is, as hot as the plugs are burning now, just reading the current plugs, you will probably shoot right past the optimal AFR and make it too way to rich. The wide band O2 would help a lot for jetting change info.
I don’t think modifying the chamber to drop the compression will result in any gains in flow or power on a stock head.
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