The final monster of the XPH: a psionified version of everyone's favorite snake-people. There's variants for all three of the MM1's yuan-ti, which I'll go over one by one.
The 4 HD pureblood originally got +0 LA, for being boring but barely acceptable tier 4ers. I'm not sure if they'd make the cut for +0 LA if reviewed now, but the psionic pureblood's way better magic (at-will Psionic Charm, at-will Psionic Daze, various 1/day save-or-loses) make me believe that those at least deserve +0.
An impressively wide range of PLAs, but this still suffers from the halfblood's original flaws (grapple attacks, but with 7 HD and no better physical strength than an orc). It's worth taking over the regular version, but still -0 LA (interested in arguments for +0 LA though).
9 RHD and some bigger SLAs (up to 1/day Baleful Polymorph) to go with it. Honestly, this should work at +0 even if it's on the lower end.