I have competed for YEARS. I've held an IFBB pro card for the last 16 yrs so I think I might know just a thing or two on the topic.
I stand by the advice I already gave. To gain muscle mass sometimes you'll have to gain a little body fat then diet down. Most people think they are hitting a plateau from the AAS they are using when the issue is really they are starving themselves and don't realize it, or they are over training or both.
I did that for years because I was so paranoid about gaining any body fat at all. Once I learned if I consumed more calories, cut down the cardio to only 3, 20 min sessions a week while bulking up and only training no more than 2 muscle groups per training session, I went from a hard gainer at 5' 9", 185 lbs 8% b/f to 265 lb 10% b/f in 16 months!
That year I placed 1st in 2 local shows which qualified me for the NPC USA show the next year. I placed first in the USA Heavy Weight division and second place overall and won my pro card. I came in at a very shredded 230lbs!
So take the advice for what it's worth. I've been where you are. Either listen to the advice of veterans and learn or justify why you can't seem to get above 163 lbs @ 5% b/f being 5' 9".