Please bear with me as I am a complete novice concerning Porsche

I'm not even sure if this is the right forum to ask this question, but I'll give it a shot anyway. I've become quite obsessed with the 911 and have tried to do as much research as I can before buying and I'm reading some information on certain model years to avoid. I found a 90 coupe, actually for sale on this forum, that's in really nice condition but apparently the 90-91 911 had some issues being 1st years of a new generation and I was told by a Porsche dealer to avoid those cars. I also see where the 99-01's apparently had some quality issues which may explain why they are so affordable compared to other model years. Are these naysayers correct or are the quality issues overblown? I am looking to buy soon but don't want to go in blind and make a costly mistake. Any inside information on this would be greatly appreciated. Thanks