I have a performax10/20 and I have two pieces of maple I am running through to glue up a riser with a stipe in it. I ran both through several times taking off a little at a time to square them up and get a good mate (glue joint) and when I hold them up to the light they are touching on each end and a gap in the middle the are each roughly 16x1.75x2.
Any ideas as why I would be getting this?

Did you run them both through at the same time?  I assume that you switched them end for end every few passes.  I too have that sander, but use a joiner for that job.  Never tried to do that with the sander, of course I had the joiner before I got the sander.

Yes and yes. My buddy has a joiner I may try.

Probably a slight bow in the wood. A drum sander will sand with the bow and will not square it up.
Jess is right. Square up your block before you sand it on a joiner.

Thanks guy's

It sounds like A WARPED BOARD.
What does it mic. at the ends and along the entire length?

If you don't have access to a jointer, run it through the table saw and take a blades width off to square it up, then a run or two through the sander to take off the blade marks.

Also check for snipe on the ends of the boards.  I know mine does that quite a bit, so I leave everything long and trim after.

Yea I noticed if I run a shorter board through I can get snipe so I just place my hand on the wood at the out feed over the belt.
I'll mic it and see where it is at, then I'll run it through the table saw to square it if needed.

Take a straight edge and put it against the board on both sides.  That will show if it is snipe or a warped board.  If warped go with the table saw squaring.

If it was snipe wouldnt it touch in the center and not on the ends?
I put a straight edge on it and it shows the same thing, touching on the ends and light in the middle.
I ran it though the tablesaw and it didnt change??? I dont get it..

Please.... go to your buddy's and use the jointer and square that board up!! LOL Set it to barely take any wood off and work one 90 degree at a time.

Van thats my plan sometime this weekend.
I'm sure that will work.
Add to want's/needs list,
(one Jointer)