Hi Colin,
"OK,But could it really detect the difference between the power of a 150psi compression stroke and a 220psi stroke?"
Yes and it will detect a lot less too.Remember the engine speed on a compression test is alot slower than when running so is not a true reflection of mechanical operation of the valvetrain with sticky valves etc
(assuming that there actually is NO electrical misfire).The system did not report an electrical misfire ie "Launch says p0301 cyl 1 misfire detected"
The p030x codes are not electrical misfire codes,the system is reporting a general engine misfire which can be fuel,ignition or mechanical based.This is why I said to go back to basics first.
Hth Sean