There are seven L.E.A.F. suit upgrades that must be acquired during play. The energy upgrade modules are NOT part of this achievement—They have a separate achievement named “Full Power”. All suit upgrades are found in the large crates discovered along the storyline pathway, and it is unlikely any will be missed. That said, most players will complete the game and not have the achievement. The reason is that the (presumably) last upgrade is locked away behind the second pyramid door, and a total of 70 medallions are required to open it. So, once the “Relic Collector” achievement pops, head to the pyramid and collect the last suit upgrade.
Fortunately, two fellow TAers have provided aids to finding the medallions and other achievement related items:
—psymon has posted a three-part, 3.5 hour (!) YouTube walkthrough showing all the crate locations, acorn doors, etc. herehttp://www.xboxachievements.com/forum/showthread.php?p=68132...
—Texans2K2 has a checklist of all collectables by area in the TA guide for the Full Power achievement, plus images of the crates are linked in the comments section, here
The Full Power achievement in Valley worth 243 pointsCollect all energy upgrades
For nitpickers, there actually is an eighth suit "upgrade" (a skin), hidden in a cave in the first area. It cannot be reached until the "water walking" upgrade is acquired. It has no power and is not needed for this achievement, so I guess it would qualify as an easter egg. I will not spoil anyone's fun in searching for it by saying anymore!