PLEASE HELP!

On Crash Bandicoot 3: Warped (for ps2) I've got all the crystals, all the blue relics and 43/44 gems. The gem I have not got is on the level Sphinxinator (I think it's level 21) No matter where I go or what I do I just can't seem to get all the boxes, I end up with 101/105. I've gone the way across the big hole at the beginning and come back the other way to get the boxes I missed. Then I went the normal way and got all the boxes, the bonus level and even came back again to go on the blue gem trail but still no luck! Can anyone give me any tips or tell me how to do it? Thanks :)

Oh yes and I've read on a few websites that to get another gem by talking to Cocoa is this true?:confused:

Actually it's for PS1 not PS2 (sorry :o)

Have you gone through the bonus

Yes! But I did it now yay! You have to go backwards and get the 4 boxes!

Walk toward the screen and you will find 4 boxes. The last 4 that you need.