Party 15 Preflop Decision (or lack there of)- 99 utg

[elmo]

For a long time I was not limping anything UTG or UTG+1 in the party 15 games. Why? I was getting myself into trouble with some suited broadways, and I've always hated playing middle PP for set value. I've progressed beyond this foolish habit, and have started limping 77-88, a9s, ats, kjs, qjs at most tables.

I used to think I was giving up too much value by folding hands like 99 and ATs utg, and since I wasn't limping it, I was raising it. For whatever reason, I don't even know what the correct play with these hands are. Please enlighten and convince me.