Ok here’s an update. I had the car diagnosed and the long and short fuel trims were way out of the normal range. Specifically long term bank 1 was 9 and bank 2 was 19.82. Forget the exact numbers for short term fuel trim but that too was definitely off.
Mechanic took off the upper intake manifold to clean carbon but upon removing it, there was not very much buildup present to actually clean. So he said we might have to continue the diagnostic…however he did notice the IMRC bushing was broken causing the IMRC arm to hang off and the butterfly valve on the drivers side to be stuck open. He put on a new bushing and put the arm back into place ensuring proper operation of the butterfly valve. We cleaned the small amount of carbon there was off anyway from the EGR passages In the lower intake and cleaned the upper intake passages too. Installed it back, and then did an induction service with seafoam to clean cylinders and pistons from carbon. Finally put a new set of oem spark plugs. After doing all that and driving it, the long and short fuel trims were back in normal range fluctuating within 5% of zero. This SHOULD fix the problem right? The fuel trims being off should be what was causing the spark plugs to foul with carbon right?