Apparently ECL and LA are gone with Pathfinder. Take a look:
http://paizo.com/paizo/messageboards/paizoPublishing/pathfinder/pathfinderRPG/rules/noMoreECLJames Jacobs (Editor in Chief):
"ECL is not a part of the Pathfinder RPG. Nor is LA (level adjustment). There's some discussion in both the PRPG and in the Bestiary about what to do if a player wants to play an unusual race, but the application of easilly-abused rules like ECL is no longer a part of it.
Of course, if those rules worked for your group, the game's compatible enough that they'll still work with PRPG. And eventually we might do a "Savage Species" style book that goes into deep detail on how to deal with PC races that deviate far from the norm. But honestly, with the increase in power to the base races, any of the previously-known-as-ECL +1 races should work fine hand in hand with the standard PC races.
EDIT: The Council of Thieves Player's Guide has a fair amount of advice for how to use a tiefling as a PC race. It's a free PDF, so you can download it and use some of the advice or solutions there for other races pretty easily."
Has anyone seen this Council of Thieves pdf??? I'd like to get my hands on that. A tiefling would be a kickass character in 3.x.