Just realised that I am in Return to Peru instead of Olmec Valley. No wonder the walkthrough didn't make sense. Does it matter if I play that now? If it does how do I get to Olmec Valley. Shouln't I have bought the map. When I did it said I was going to a secret level. Thanks anyone.

There are different opinions around about this. I actually played the game four times now and each time in the last level I suddenly had a lot of ammonition and health packs. I think this is some kind of bonus which may depend on if you've found all the treasures before or not.

Now, if you don't spend the $2500 for the secret map you automatically return to peru after you've finished the last level #16 (Aetherium). Then you get the named ammo/health bonus there.

However, I personally think that the ammo/health bonus is much more useful in Aetherium since this is really a difficult level. So I recommend to buy the map prior to Aetherium so you spare those many ammonition and health packs for Aetherium.

Hope this helps. Good Luck!