car cranks, wont start, boosting works

Car cranks, but won't start unless it get's boosted. New battery from May
2022 purchased and installed within an hour August 10th, never touched
ground. Battery shows 13.41V. Spark plugs changed for DENSO iridium
plugs SKJ20DR-M11 in late June 2022. Faulty knock sensor SBC3655
replaced In June 2022 and therefore turned off the check engine light. The
car was running great before and after both replacements. Previous 2 years
old battery had 12.43V could crank, but couldn't start without boosting. The
problem appeared August 6th. The car was driven irregularly (once or twice
MAX every week) in July. During this time, cranking got slower but turned
over. After boosting the car, it runs without any issues. No misfire, no jerking,
no hesitation. Fuel tank full of standard gasoline. Goes upwards of 6 000
RPM. K20a3 engine.