ANOTHER WAY TO TEST FOR A VACUUM LEAK IS TO SPRAY CARB CLEANER ON THE VAC LINES WITH THE MOTOR RUNNING.
IF THE RPMS INCREASE... THERE'S YOU LEAK. YOU CAN USE OTHER FLAMMABLE SPRAYS, BUT I FOUND THAT CARB CLEANER WORKS GOOD.
ALSO, THERE'S THE PCV VALVE THAT IF IT GETS CLOGGED CAN CAUSE A CODE TO POP. IT IS RECOMMENDED TO CHANGE YOUR PCV AT EVERY OIL
CHANGE. WHICH FOR 3 BUCKS IS WELL WORTH THE HASSLE.