ok i fixed it and this might help others too.
I found that multiman will take the split files when running off the external and reform them on the internal (even though you are on the external) so when you are not playing those games it is worth deleting those giant files which in my case were 10 gig and 12 gig.
Even if you want to play those games as long as they r on the internal they will run fine.
you only need the multiman cache stuff is you are on external and they are split file games (which it will tell you in multiman next to the game title). I think this is right and it worked for me.