Slthatch

Hey guys i recently purchased a 2001 saab 93 se. 150k miles with codes 1334 and 1312 displayed. The dealer i purchased this vehicle from told me these codes are from them installing incorrect spark plugs, however i feel it may be a bigger issue. The car runs great but i cant find any info on the importance of correcting these codes. I understand they're related to misfires in cylinders but the car seems to run fine, whats the threat of not fixing these codes?